Soldier Games

Soldier games mostly put you on your own against numbers that don't make any sense, and then they make that the appeal rather than the problem. You're outnumbered because it's more fun.

One Man Army: Battle Game says it in the title. Shoot & Sprint: Warfare keeps you moving so standing still is never the answer, and Hunter Hitman slows everything down into something closer to a puzzle about positioning. Get To The Chopper gives you an objective other than clearing the map, and My Army Base steps back from the shooting entirely to let you build the thing instead. None of them ask for much setup, so you're into the action within a few seconds of the page loading.

There are 5 free games under this tag, all playable in the browser with nothing to install, and the variety here is wider than the label suggests.

The gunplay is in Shooting games, and Combat Games is the tag for anything built around a fight.