I've caught myself saying WTF lately in my offline life. Funnily enough, I don't use WTF online, but around the house I'm spouting those three letters all the time.
When I tell you I say "WTF", I literally mean I say "Dubya Tee Eff". It's a great way to express yourselves with kids in the room. It's swearing without the swear.
I've actively fought against IM-speak, but I think there's something quite hilarious about using IM-speak in daily off-line conversation.