Blizzard have released a new custom 3v3 map for StarCraft 2 called Burning Tide. It's got a new, resource-hoarding objective, collectible resource caches, and rising lava tides. The best part is that it's already in your map list.
It's a "greed" game type, which means that you're competing for resources against the enemy team. Once either team reaches the resource target, they win. If you're very skilled at StarCraft 2's multiplayer, hoarding resources will do weird things to your brain.
I tried playing against two medium AIs just there and they focused totally on minerals, accruing 10k before I was ready to rush them with mutas. I suppose you could have two of your 3 team mates focusing on attack, and have the third just pumping out harvesters and quietly teching up. Obviously, deciding between stockpiling your own resources and spending them on units to keep pace with the arms race is a vital balancing act that makes Greed so fun in RTS games. This one has deep fried Zergling in it, so it's 1% better by default.