One of my favorite custom SP maps is cleanup. If you don't know what it is, it's a level where you play as the covenant and you fight the flood and the humans. There were some new weapons and vehicles in the map, but it was mostly all Halo 2 stuff (Energy Sword, Specter, Carbine). It wasn't too short either, no offense polar, but Biohalo was pretty short. I liked the new scenario of the map and the fact that it was long. However, I didn't like it that there was one part that you have to run through because it's too hard to fight everybody that's there.