The only company that doesn't spank you for usages is T-Mobile. Their FUP on the standard contract is 3Gb per month, and they'll tell you off for the 1st month if you break that. 2nd month they'll send you another letter, and limit your speed. The 3rd month they'll drop your speed, and it'll stay there until you upgrade to the 7Gb package.
All of the others charge small fortunes if you go over the limits. Also, for gaming, it's not the speed, it's the latency that will effect you. Latency on those things is terrible. I use mine for browsing and a little media streaming, but that is all.