Sure. There are quiete many. Lakerbot is pretty famous, even it is not that good.
Spiterbot is the best Q3-Bot i've played against.
He has human-type aim (ok, master on skill 100 has inhuman aim ;)), he can time items (a bit), he can strafe jump to reach high platforms (he needs mapinfo on a map, containing places where he can strafejump) and he evades incoming projectiles quiete well.
I am not sure, if its supported in OA. I guess it'll work only on Q3maps as ztn3tourney1, pro-q3tourney4, pro-q3dm6 only. (Unless you create a map-file for the map).
You can get it here