It doesn't even have to be what you would really be, it's what you WANT to be. So here are the classes, and if I miss any job description then just add it.
The strongest fighter. You're usually awkward outside of a fight, and quick to take offense at any small insult. Still, you're the de facto 'leader' of the group, and you always mean well, and you always come through for your friends.
You skill varies, but you're basically the more analytical fighter. You're Either protecting the rest of the group or supporting the Primary. You're also well suited for more social environments. You're dedicated to your friends and would gladly give your life to protect them.
You are the one who knows how to fight, but usually does it just to buy time for the primary or secondary. You also usually fall under the category of secondary.
Usually not very adept at fighting, you take care of the others' injuries, and provide vocal support. You also may provide some minimal combat support from a distance, but as you are usually the one being protected, this is often unwelcome support. Still, when your friends are in danger, you can kick into high gear and dish out serious punishment to your enemies.
You're big. You're bad. No one tells you what to do. You do what you want, you give the orders, and your trying to take over the world. The problem is that pesky primary fighter and his/her group getting in your way. You know that at some point you'll have to fight them because they'll always be in your path for global domination.
Personally, I'd probably be a secondary, because, not to think too highly of myself or anything, I'm a fairly competent fighter (I think) and I take awhile to get angry. Still, my philosophy is to end the fight quickly and ruthlessly, so that may qualify me for primary. I based my class descriptions on InuYasha, so if any description is lacking, tell me and I'll change it.