A lot of people use Fraps...
If you are recording however, then I would recommend Mirlis Action! or dxtory as they produce the same quality as Fraps whilst losing only couple fps max...
I agree with Jared, with a tiny exception for Mirillis Action! Both DxTory and Fraps allow you to record your video un-compressed whereas with Mirillis Action! you're forced to at least use FICV (Fast Intra Compression Video -- Also an anagram for fVic
). So, if you want the absolute highest quality recording, I'd suggest DxTory since it allows multi-core/threaded video capture to multiple hard drives simultaneously. The only feature I don't think it has compared to Fraps is Stereoscopic 3D video capture.
In summary, if you want the highest quality lossless recording at the highest performance, use DxTory, otherwise use Mirillis Action! if you want the highest performance with high quality video compression ( Mirillis Action supports IGPU assisted video encoding of MP4/H.264 video on 3rd Generation Intel Processors with Intel QuickSync). I would only use Fraps if you wanted to capture Stereoscopic 3D.
I use Mir. Action and I agree, it's a great program but you have to do this funky encoding to get it to play right on regular players. Maybe Im doing something wrong as it can record as .mp4. I do like the in-program encoding options as there's a ton of them.