Title says it all really :)
Dancing...horizontally...naked, in bed with my hubby. Hiking would be my very distant second choice.
Me? Just a few examples are: cooking with music and singing horribly along, breaking into bad dance moves between lifting sets, skipping to coffee, chasing after the dog, chatting up farmers at the greenmarkets, taking the train to a new stop and wandering around. Getting a Zipcar for the day for a random adventure to hell knows where. Organizing books by colour instead of alpha or by author. Attempting to make the bed military style to see if, really, you can bounce a quarter off of it.
Why have a certain activity? Life should be play!