Once i was into a server and there was something like tribes, it was freaking awesome.
There was 4 teams: water, air, stone and magma, each team had it's own building to their respective attributes. example:
Water team had a town under/above the water.
Air had a floating town (hard as fuck to come there)
Stone was underground
Magma was in the nether.
Also wars, they were awesome (without griefing).