A couple more:
Diffuse/defuse. You do not want to diffuse a bomb, trust me on that one.
Carmel instead of caramel.
Text speak. (replacing words with numbers, shortening words to single letters, etc.)
Capitalizing the first letter of every word, or every other letter. Especially irritating when you're trying to roleplay and one of the participants will not stop typing like that.
All of the sudden.
Use to be.
Case and point.
Baited breath. (Fishy!)
...No, I don't twitch a lot. Why would you ever think that?