My little nominations list:

Single Player: "Episode Five: The Fortress of Ruin" by EvilMike
Tileset: "Casualty Mines" by Gus
CTF: "Mt. Helens" by Superjazz
Battle: "Rainforest Revelry" by OLC
Pack: "Planetary" by FawFul

Yep my list is kinda shortened, as I haven't been active enough to check every release. I've experienced most of the levels through public and private servers, no reviews or ratings.