Let's face it. One of the pleasures of role-playing is getting into a brawl. After all, unless you are a boxer or maybe a soldier, you don't often have the opportunity of a good fight without unpleasant consequences... and even if you fight for a living you can get hurt even if you have sufficient reason not to get arrested!
So, if you are finding that your game is overfull of role-playing everything else, you might want to take a look at this: a bare-bones (if not bare knuckle) combat system with just enough bolted on to be a role-playing game rather than a combat simulation.
It dives straight in by making basic characters. Eight attributes and a neat mix of choice and chance to get your values: you have 21d6 to distribute between the attributes, and then you roll them to get the actual values. The value you get determines what die type you use for that attribute.
To do something, you take an action. If you are brawling, that action will be opposed by whoever you are fighting; if you are doing something else the 'opposition' is based on how hard the task is to accomplish - which gives a die type which is rolled against your roll (based on the appropriate attribute). Simple so far... then there are a few options like targeted attacks, protection, surprise, etc.
The discussion moves on to gear, which will naturally depend on the genre in which you are playing so there are sections for fantasy, science-fiction, modern warfare, post-apocalypic and spy thrillers, followed by a section on playing as the monsters.
That's it. Simple and straightforward brawling. It's all written in a casual, chatty style but gets all you need to know across clearly. So for those days when you want to role-play without the frills, create a quick character and get your fighting face on.