I can only imagine how much cardboard that would take...

Quote from Dudeman.

I was talking about when 2 people spawn together and over power a single enemy one at a time.

This is almost completely impossible to avoid without adding spawn-in invincibility, which is a bad idea because it's too easily exploited. It has nothing to do with balance.

Swords are absolutely unbalanced when you crouch because you dissapear off the radar. It's impossible to dodge if you're not playing a monkey. If you take ever corner slowly, then he can just charge you or set up another ambush.

This is where level design comes in. Try and find a perfect corner with no way for someone to attack from behind or toss in a grenade first. Also, when you hang out there, your position is forsaken, so people will know to exercise caution around that area. Along with that, though, experienced players know where the better camping corners are, and so are able to prevent such a death.

Battle rifling is easy btw. It also ruins the balance. Most players (who aren't savy) just stick to the assault rifle and charge people with it and go for the melee. How do we stop that????? Give them a better gun when they spawn >.>

Kill them first.

You're not looking at balance past weapons. There's a great many more things, like level layout, equipment, and grenades, plus power-ups and movement strategies that help in firefights. A well-balanced game is one that only skill influences the outcome. Watch any game between skilled players and you'll see many comebacks and weapon theft because of superior skill and strategy, not just having the rocket launcher.