Glory In The Arena is a set of rules for playing gladiatorial combat with 54mm figures.
Pharaoh Rides To War is a set of rules for 20mm battles between Egyptians and Assyrians.
Caveman Clash is a set of free wargames rules for playing skirmishes between cavemen. There also are paper figures if you don’t happen to have cavemen available.
There’s been an update for the free basic rules for Impetus, a set of ancient and medieval wargames rules.
The Jackson Gamers offer Ancients By Ral, an ancients version of the venerable Rules By Ral system.