"Laugh To Myself" - because not everything funny warrants a LOL; also, more suitable form of laughter when at work or the school library where 'laughing out loud' is frowned upon; and, let's face it, LOL is played out and just all-around obnoxious.
Friend - "wut up?"
Me - "nothin. bored at work"
Friend - "at least you have a job"
Me - "LTM"