Previously in blog land I wondered if how people express their amusement offered insight into their personality. My original answer still rings true. I'm a funny haha kind of person. However...
New to the scene is "hee." Amazingly cute, my boss says this to express her sheer sense of bliss with the given subject. Although this isn't used in terms of funny, but in terms of a passive "how cute!" I love it, though when I tried it on it didn't feel right. It felt a size too small... but I think I'll try to squeeze into it.
THe sizes of expression ...
Small - hee
Medium - heh
Large - ha
Xlarge - haha
XXlarge - hohoho (heh. or maybe I'll upgrade that to a "ha" - it's a santa joke. now that's funny.)