The only one that comes to mind was this pretty generic shooter Combat Arms... haven't launched it in years though
CombatArms had one massive glaring flaw. Their complete inability to do anything about even blatant hacking. Which was a pity because it was actually a quite enjoyable game.
hacking ruins pretty much every online game though but it's of course worse when everyone has free access to servers and whatnot
Battlefield 1942
First map was free. Very, very fun times playing that, so many times had it completely memorized.
World of Tanks, Rift, Spellweaver.