Should I just punch someone? I think that might get a bounty for that.

It comes up in speech options for me.

So with one guy who works on the stables, I asked how he felt being outside the city walls with the dragons about, and he challenged me to a brawl to prove he wasn't fussed. There have been a few others as well, like one guy who I wanted to stop pestering this woman, and there was a chance to intimidate him. The intimidation didn't work, so he called my bluff and a brawl started. When it's specifically a brawl like that, no one else gets involved and you don't kill them (just don't take out a weapon or spell!). When their health goes, they just crouch and then accept that you're the winner.

[edit] I'm really not sure what would happen if you just decked a guy for no reason, but I'm assuming that it would be classed as assault/a crime because there was no provocation or anything like that.

Nope, you'll get bounty that way. Talk to NPCs, mainly at the taverns. There are many who are willing to brawl with you if you disagree with them from something. Look for these in all the locations where you possibly go early in the game: Whiterun, Windhelm, etc. I haven't even visited nearly every capital yet, and I've still found around three brawlers. My Nord sure can get himself into manly Nord trouble. Some quests can also lead to bar brawls; I've done one of these.

That's true. I also love how for the most part if you beat them in a brawl, most have said "you've been a good friend to me". Really? All I've done is beat you up. Oh, Nords and their strange ways of showing affection.

Enter inns with some swagger and just be a bastard. Eventually someone will get tired of you and call you out as a common dandy. It is then you must defend your honour.

Short version, talk to someone who looks like a scrapper in an inn, be rude to them.

Yeah. In some aspects and places, this fist-fight thingy as the test of strength is still kicking here in the north in real life. Usually there is nothing personal in it, or at least not after the fight is over. Lots of alcohol is always involved, and these brawls usually result a night in the drunk tank.

I've gotten in a couple of brawls to date, but I'd like to know if there is any questline associated with bar brawls. Nord Fight Club anyone? Anyone?

Too organized. Should be a low-life tavern with bad reputation with its unofficially "ranked" tough guys. Would suit Riften perfectly.

Thanks guys!

See that's what i thought my first hour into the game. So I unequipped my weapon and punched a bard in the face. Turns out he had a friend who had a mace >.>

you could say the bard had a amacing friend ;3

He gave me a hell of an amacing face reconstruction xD