It's not exactly a funny typo, but I see a lot of people do "o2o" and ":2" when trying to do o3o and :3. I've done it before a few times.
Yesterday on Facebook, I told my friend that I was sick and she said that she hoped I felt better, and what did I say in response? "I won't buddy :3" I did a face smack after wards, I was supposed to type "I will buddy" not "I WON'T buddy." That was embarrassing.