SHA-256

[crackbox]

I actually haven't found a GPU cracker that can do it, everyone seems to just want to do sha-1, but comparing the complexity and looking at different benchmarks here, http://www.cryptopp.com/benchmarks.html it looks to be around 30% slower, so even if your implementation is only %50 as fast as sha-1 and I get 1.7Bilion on (4) 295gtx's against sha-1 thats still a lot faster than any cpu.