I like ProtoShares, because it's really only CPU coin.
All cpu coin as XPM, QRK, SRC and other you can dig them with a GPU.
Even MMC creators said MemoryCoin 2.0 would be resistant to GPU, but now it has a GPU miner and the difficulty jump to the sky.
Try PTS mining on ypool.
Primecoin and Datacoin cannot be mined with GPU. It is impossible right now gpu mining for them to be more efficient than CPU