Go for a run
Do some vigorous exercise
Try yoga or Pilates
Eat spicy food - try a vindaloo curry
Listen to music
Dance
Sing or play an instrument
Give someone a hug
Go bush - go hiking or camping
Have a good laugh
Do something that scares you (within reason - I'm scared of sharks but that doesn't mean I'm going to go swimming with one to get a natural high)
Eat healthy food
Eat chocolate (not too much)
Do something nice for someone
Play frisbee with a friend
Bag a bargain at the shops
Go for a walk on the beach
Go swimming in the ocean (watch out for sharks)
Play with a puppy
Swing on a swing
Watch the sunrise or sunset
Make something...