adapted from here. ones i particularly enjoy are italicized and ones i super super love are bolded.

• Abduction as seduction (beloved captives)
• Accidental stimulation (proximity and friction; involuntary arousal; situations of adrenaline and reflexes)
• Anal penetration with foreign objects
• Anal sex (face to face, from behind, bottom riding top; standing; bent over desk; gay or straight; girl-on-boy with strap-on; girl-on-girl with strap-on)
• Anal/butt plugs (during sex; worn under clothes in public)
• Asphyxiation (asphyxiophilia; autoerotic asphyxiation; scarfing; choking; breath play)
• Ass-play and/or fetishization (ass lifted in the air for penetration; emphasized by harness or blue jeans; ass slapping; spreading cheeks; rimming)
• Attention (singling someone out; treating someone specially in front of others; making a point of showing respect to or interest in someone who doesn't usually receive it; observing, studying, or analyzing someone to understand them)
• Bad boys (punks, rebels; see also Rogues)
• Bad girls (dirty girls; naughty schoolgirls; femme fatales)
• Bar and club scenes (dancing, cruising, etc)
• Baths and water (tubs or jacuzzis; hot springs; bath houses or steam rooms; the ocean; swimming pools; see also Washing; Shower sex)
• BDSM
• Begging or offering (begging or pleading for mercy, for sexual release, to be taken; a character offering himself; neediness)
• Beloved enemies
• Beloved hostages (royal, diplomatic, or business hostages; see also * Abduction as seduction)
• Biting (marking, nipping, chewing)
• Blindness
• Blow-jobs (oral sex, fellatio)
• Body fetishes not listed elsewhere (ears, collarbones, cheekbones, bare feet)
• Bondage
• Bruises and other wounds
• Claiming or establishing ownership (private or public; by gesture, word, or ritual; with sex; with a collar and leash; with scent-marking or by biting)
• Clothes fetishization (e.g., uniforms; thigh-highs; stilettos; tuxedos or GQ wear; wearing each others' clothes)
• Clumsiness (awkwardness; overeagerness; during sex or in general)
• Cock and/or ball torture (whipping, stretching, catheters, etc)
• Cock bondage (cock rings; harnesses and straps; leather ropework)
• Cock worship
• Collars (slave)
• Coming in one's pants
• Coming in or on one's partner (in ass or mouth; in hair; on body; on face, i.e., facial)
• Coming quickly (premature ejaculation or knee-jerk reflex response)
• Coming without being touched
• Courting and dating (courtship rituals; dating; blind dates; personal ads; traditional gestures such as flowers and chocolates; unusual gestures designed to win someone's attention; showing off or displaying prowess; rivals seeking a character's favor; see also Seduction)
• Cross-dressing (voluntary, if reluctant)
• Crying, sobbing (erotic and non-erotic)
• Cuddling (see Touch)
• Cunnilingus
• Dating (see Courting and dating)
• Deep-throating
• Delayed gratification
• Depilation (waxing, shaving)
• Dildos (dildo gags; harnesses; strap-ons)
• Discipline or punishment
• Discomfort during sex (rough edge of a table as counterpoint to pleasure; cold stone versus hot flesh; position is uncomfortable at first but then becomes perfect; penetration is painful, then pleasurable)
• Domesticity (moving in together; nesting; shopping; building a family or meeting the family; getting a cat or dog; kidfic)
• Dominance and submission (See also Submission; Servitude; Master and slave, etc)
• Double penetration (anal, vaginal, or oral)
• Erotic torture
• Exhibitionism
• Exposure (with or without eroticism; feeling physically exposed, such as with legs open; a woman's shirt being opened to expose her breasts; characters being forced to undress in public; someone opening a door on people having sex)
• Face-fucking (blow-job)
• Face-sitting (straddling for blow-job or cunnilingus)
• Fake rake (a man falsely rumored to be promiscuous, who isn't; romance novel term)
• Fantasies (shared or solitary; role-playing)
• Finger-fucking (as preparation, foreplay, accompaniment, or main act)
• Flirting (conscious or unconscious; with glances or touches; banter)
• Food (feeding one's partner; romantic dinners; food as foreplay or flirting; food used during sex, such as whipped cream or chocolate)
• Forced orgasm
• Foreplay
• Friction or frottage (naked or clothed; masturbatory or with partner; cocks rubbing together; tribadism; intercrural sex; someone rubbing off on sheets while giving head or being fucked; itchiness and scratching; chafing clothes; friction while on horseback or riding a motorcycle; accidental contact)
• Gags (ball-gags, scarves, mouth bits, etc)
• Gentleness (tenderness; kindness; concern; gentle natures; characters who display sensitivity to fearful children, animals, the weak, etc; gentle responses at unexpected moments)
• Good boys (law enforcement figures; gentlemen; characters who prompt a desire to corrupt or provoke them, or to get them dirty; priests; prim schoolteachers; angels; nice guys; virtue and nobility in general)
• Good girls (nice girls; daddy's girls; schoolmarms; nuns)
• Hand-jobs
• Hot spots (a special spot that make someone crazy when stimulated, such as the vampire spot on the neck, the backs of the knees, the inner arms, navel, or earlobes)
• Human furniture
• Humiliation (erotic or non-erotic)
• Humor (funny banter, screwball comedy, etc)
• Humor as a mask (characters who hide pain behind humor)
• Ice princesses, snow queens (cold characters who may or may not succumb to melting; need not be female)
• Immobilization and/or helplessness
• Intercrural or interfemoral sex (i.e., thrusting cock between partner's thighs)
• Jewelry (decorative and/or symbolic; wedding rings; earrings; slave bracelets; piercings)
• Kissing, necking
• Loss of control (emotional, physical, situational, erotic, etc)
• Love and passion (falling in love; love at first sight; one true love; eternal love; unconditional love; star-crossed lovers; tempestuous passions)
• Love/hate relationship
• Make-up sex or reunions
• Masks
• Masochism
• Masquerade (a character pretends to be someone else, or something he's not)
• Massage
• Master and slave (erotic or romantic slavery, or otherwise)
• Masturbation (solitary or as performance)
• Messiness and markers of arousal (mussed hair; flushed cheeks; swollen mouth; displaying bite marks or hickeys; clothes in disarray; sprawling; come-spattered skin)
• Mindfuck, mindgames
• Mirrors
• Multiple orgasms (See also Sexual appetite or excess)
• Multiple partners (sequential/serial sexual encounters; orgies, gang-bangs, or group sex; puppy-pile cuddling; see also Sexual appetite or excess)
• Neck fetishization (nape of the neck, throat, hickeys, etc)
• Oral fixation or fetishization (lips, tongue, or whole mouth; french-kissing; licking; oral displays using food or beer bottles; smoking cigarettes, cigars, or pipes; biting or chewing one's lip(s))
• Orgasm denial
• Pain (with or without pleasure/endorphins)
• Pampering (spoiling someone rotten with gifts or money; physical pampering such as massage and grooming; giving someone a novel or unexpected degree of emotional or sexual care; catering to someone's every whim, e.g., someone who is in the hospital; harems as settings for pampering)
• Patience (e.g., showing patience toward a character who is brain-damaged or who is struggling bitterly with being recently crippled; or to a character prone to irrational fear or outbursts; patience with children; see also Gentleness)
• Penance or reform (bad boy turns good; evil seeks to change; performing acts of atonement or restitution; self-mortification; martyrdom; selflessness; apologies or apology sex)
• Pillow biting
• Playing hard to get
• Pornography (magazines and videos; character was previously a porn star or fluffer)
• Power issues (inequities in beauty, rank, or class; power games; BDSM; power reversals; sheikhs, sultans, princes, and other royal figures; teacher/student pairings; magical powers; abuse of power; blackmail; romantic slavery; liege/lord pairings; issues of respect; sexual scenarios such as a dominant character giving his partner to others to use, or a character kneeling beneath a desk and blowing someone who's on the phone)
• Preferential treatment (e.g., making a point of showing respect towards someone when no one else does; showing a soft side only to them)
• Prostate pleasure
• Protectiveness (physically or verbally defending someone; caretaking in general; big guy/little guy pairings; bodyguard scenarios; mysterious benefactors or protectors)
• Public displays of affection, PDAs
• Pushy bottom
• Restraint (pinning someone down; pushing someone's arm up behind their back during sex; covering or clasping someone's hands to prevent movement)
• Restraints (handcuffs, leather ties, chains, etc)
• Reversal of role or fortune (loss of love, power, rank, etc; hunter becomes prey, master becomes slave; a strong character is made weak; role-reversal games; Flowers for Algernon scenario)
• Ropework (intricate/artistic erotic bondage)
• Rough sex (quick and dirty sex; hate or grudge sex; angry sex; fighting/wrestling; jackhammer fucking; sex with no or little lube)
• Sadism or sadomasochism
• Sandwich sexual position or chain fuck (threesome)
• School themes and fetishization (boarding schools; dojos; scholarly gowns and uniforms; sailor fuku; prep school chic; teacher/student pairings; donnish or professorial characters; prefects/head boys; caning; schoolboy hijinks or sexual discovery; military academies; tutoring and teaching in general; see also Conditioning)
• Seduction (one-on-one; two-on-one; verbal or physical; intense erotic courtship or teasing; see also Courting)
• Sensory overload or enhancement
• Sex in public or semi-public places
• Sex in vehicles (cars, taxis, limos; planes or space shuttles; motorcycles; carnival rides)
• Sex is interrupted
• Sex on, against, or under furniture
• Sex outdoors/outside (in a field; in a rainstorm; with snow falling; on the beach; in a graveyard; in an alley)
• Sex standing up (including against a wall)
• Sex with clothes still on or partly on
• Sexual appetite or excess (hypersexuality, i.e., high sex drive; sex addiction or compulsive behavior; short/no refractory period; multiple orgasms; multiple partners; indiscriminate sex or sluttishness)
• Sexual frustration (orgasm denial or being unable to come; blue balls; enforced abstinence; self-denial; inability of two people to touch)
• Sharing (sharing a beer bottle, joint, or bucket of popcorn; loaning someone clothes; a character letting someone stay in their home; sharing confidences; sharing a woman/man)
• Shower sex
• Sixty-nine (69)
• Size queens
• Slow and/or prolonged sex
• Smarm (intense friendship with physical closeness but no actual sex)
• Spanking (over the knee or lap, etc)
• Spooning
• Sports themes and fetishization (sports rivalries; uniforms and jock-straps; wrestling and sweaty exertion in general; locker-room or shower scenes; team gang-bangs; swimmer/surfer body types; pool and billiards games)
• Striking with implements (whips, belts, riding crops, canes, paddles, etc)
• Striptease
• Submission (obedience; submissive behaviors such as boot kissing, crawling, keeping one's eyes lowered, or kneeling for master; believing in cultural dictates of submissive behavior; abasement in general)
• Threesomes (M/F/M, M/M/M, etc)
• Topping from the bottom
• Toys and devices (sex toys of all kinds; feathers, ice cubes, hot wax, etc)
• Trapped or stranded together (on another world; on a desert island; in a cave-in; in a cabin during a snowstorm; in an elevator)
• Undressing (undressing in front of someone for the first time; one character undressing another; fumbling clumsily to get undressed; stripteases)
• Urgency for sex (begging to suck cock; desperate to fuck; greedy bottom)
• UST (unresolved sexual tension)
• Vaginal/female genital fetishization (wet, tight; virginal; aching/stiff clit; wide lips; multi-orgasmic)
• Vaginal penetration (e.g., deep dicking)
• Vaginal penetration with foreign objects
• Voyeurism and vision themes (character A secretly watches B and C have sex; character A is forced to watch B and C have sex; character A watches character B perform/masturbate; viewing one's beloved in general; taking pictures or video; eye contact, especially as flirting; establishing authority with a look; closing eyes as a trust gesture; character A feeling that character B truly sees him, when no one else does; the quality of light, e.g., characters lit by moonlight or candlelight, or gilded by the setting sun; being in the dark; temporary or permanent blindness; gazes as objectification)
• Washing (washing one's partner, body or hair; bubble baths; shower scenes; slave service in bath; cleaning/cleansing someone who's been degraded, or who is injured)
• Well-fucked (being fucked out; fuck-dazed; sated and sleepy; wrecked; softened and debauched)
• Wet dreams or erotic dreams
• Wish-fulfillment