I'd have to go with Zone Control. Good for balancing out expanding to aquire more units, and defending your existing ones. I know it's essentially StarCraft without the minerals, but it does take a considerable amount of strategy, despite the fact that it really only involves doing 1 of 3 things...
1) Build up.
2) Attack and gain minerals.
3) Spend minerals on upgrades or save for another base to gain units faster.
Upgrades are essential once you've established a few bases. Yeah, you can try overwhelming with brute force, but if your opponent is smart, than that might not always work.
Additionally, I come across fewer rigged ZC games, than say Evolves or Golems.
Personally I'm more of a ladder map player though.