Opsmp

opsmp.net is an OP prison and OP factions server, based on the name of it. You spawn in, grind ranks up through the prestige system, and buy your way to better gear and perms as you go. If you like the classic OP style of play where money and rank progression are the whole point, it's worth a look. Worth noting the address doubles as the name, so opsmp.net is really all you need to connect and start playing.