Whether as a lovable cartoon character as shown above or a grim denizen of the prehistoric past, the simple caveman can be used in so many ways in gaming. I know that I have found a place for him in fantasy RPGs and in Pulp Adventure games.
They make good minions for higher powers and they also make great encounters in lost worlds. I've used them in my Age of Stone and Bone fantasy RPG setting as a sort of replacement for orcs and goblins along side more evolved humans. We have seen them in the works of Frazetta and the pages of various Conan comics. They have harassed intrepid Victorian adventurers through the pages of fiction and on tabletops everywhere.
There are many excellent miniatures made to represent these fine fellows...
Copplestone Castings does some wonderful Pulpy 28mm cave folk
Primaeval Designs does 28 and 15mm cavemen
Eureka Miniatures has 28mm Neanderthals
There are likely more out there, but these are the ones I know of. In addition, I find that you can get even more pose variety by using some Ancient Germans from any of the Age of Romes historical miniatures lines out there. Many of these are barely dressed or even naked, making them perfect for simple conversions or not. They also have wild hair and large beards that make for very simple, primitive looks. Weapons are easily modified if they are anything more than a spear or club.
So beat your chest, grab some fire as you salute the original scruffy-looking nerf herder!