When (forever) alone:

• reading and writing
• doodling
• swimming
• molding and sculpting
• playing (but not practicing) the piano
• composing new pieces
• singing and dancing
• playing with dogs
• listening to thunder and watching for lightning
• walking around and exploring
• eating all the carbs!
• making lists :-|

With others:

• board and card games
• sports (especially if it involves running)
• sharing music
• playing Nintendo
• laughing
• tutoring
• riding roller coasters