In no particular order; Spontaneousness is good.

• Smell of freshly mown grass
• Getting new, fancy notebooks
• Reading on a rainy afternoon on the bed with a cuppa something.
• Playing an instrument you like
• Doing nothing, just thinking
• The library
• Discovering things in that old roon you haven't been in ages.
• The airport feeling
• Shoes which fit well enough to be tight, loose enough to slip into.
• Goals
• Ikea
• Nostalgia
• Suddenly great friends with someone who was just 'acquaintances'
• When you've finally solved that difficult math question
• Schadenfreude
• Encores
• Music you find moving/touching/soulful
• Star Wars
• Things that make you laugh out loud (eg: Monty Python anyone?)
• Going to someplace special. (eg: movie theatre, concert...)
• End of tests!!
• The feeling when you've just aced the subject you've always failed.
• Understanding something yourself
• Irony/Sarcasm
• Hot soup
• The smell of good food
• Goofing off
• Sleep after a hard day's work
• The sense of FREEDOMMMM!
• Sleeping after a long day
• Dancing in the rain
• Petrichor