I use fraps and xsplit. Currently experimenting with other programs as well.
Fraps is always reliable & great quality, zero lag for me. The only downside is the large file sizes.
Xsplit is great, the quality is pretty good too. The major positive about it is that the file sizes are extremely small. I can record 10+ minutes of a clip like its nothing. The free alternative to xsplit is openbroadcaster (OBS), I tried it and for some reason it lags on me even tho I have a good computer.