Lol napalm paintballs! <3

That would be soooo incredibly dangerous (because paintballs often break in the barrel), lol. How exactly would they be ignited though? Seems it would need some sort of self contained ignition system. Napalm doesn't actually explode or self-ignite.

You can actually make some crude-grade napalm by mixing some styro-foam into gasoline. Just shred a cup or something up into bits, and slowly stir it in until it's thickened and consistent (napalm is just thickened gasoline, in essence). Then you can get a good idea how a paintball sized chunk will burn. I've done it before. It's not very impressive, but will burn for a LONG time. It would probably work best as one of those weapons that does damage over an extended period of time. Wouldn't be effective against vehicles or armor though. Only humans or organic things.
Maybe you should look into some sort of thermite type weapon for anti-armor/vehicles. Thermite is basically aluminum powder mixed with FeO (rust). When it comes into contact with a flame, it burns at thousands of degrees and melts through anything it touches. You could make some "sticky grenades/bombs" that contain thermite. They could be magnetic or have a sticky substance coating them. A player would throw or attach it to a vehicle or object, and the timer would count down to ignition. When it ignites, bye bye whatever it was stuck to.

Actually old technology that's still effective today.
Oooh! White phosphorus! Lol, I'm a total pyro as you can tell. White phosphorus is one of the nastiest things ever. It's often used in shells and bombs. It burns in a semi-liquid state, and can melt through virtually anything (even through Tungsten like butter). When soldiers are hit with white phosphorus, a single drop can literally eat through your entire body and kill you. They would have to use a dagger or bayonet to dig it out of themselves or a friend. You could literally put a burning hunk of it on the right place on someone's shoulder, and it would eat all the way through them and come out the bottom of their foot. Yuck!

It will go through practically any armor, buildings, the ground, lol. It's terribly nasty stuff.