Well, I say "yo, dude" in a joking way, or "...duuuuuude..." when I think someone's said something stupid, but I don't say it too often, it's not really a word I like to use. Also, "bro" and "man" aren't really...well, I don't like them, and that's that.
I mostly call people "fool", which isn't nice, but once I start saying it as a joke I keep it as an actual nickname for people.
Also, seeing as I'm a scouser, I've started taking the piss out of people with the same accent, by calling them "ming", which is...embarrassing, to say the least. Some of the words people use these days, though, my god...