Column, Line and Square was the first set of Napoleonics rules that I ever played — and I suspect, the first set that many people played. We called it Column, Line and Slaughter, though, becuase slaughter was the usual result.
Still, it was fun to play –especially with 25mm figures.
Sadly, the set is apparently no longer in print. But you can get the rules here, free for the downloading.
GrimDark Racing is a set of simple rules for races in the Warhammer 40K universe. Just use models you already have. There’s plenty of violence, of course.
The Fast Play Rules for the Seven Years War. The author writes:
These are fast play rules for mid-18th century battles with 15 mm figures, the focus is on playability. They are ideal for campaingnplay, where you would want to finish the battle in one or maximum two hours. They are not suited for historical refights.
Bob Cordery offers Redcoats and Natives, a set of free wargames rules for the colonial period.
Panzer Troops is a set of free wargames rules for WWII battles. The rules are intended as an introduction to historical wargaming.