Pawn Tactics used to be very active. There were many full rooms of various maps, and many exciting battles occured. From 24 man citadel, to 24 man conquest - many full games have been enjoyed.
I started out PT playing only Turmoil because that room was always packed with 20-30 people. Then I switched to playing mostly conquest to pad achievements easier. After the game started dying I just played whatever maps had players, usually Bloodshed and LI.