memtest for GPU's
 

I suspect I may have a memory problem on my GTX680 (games continuously crash). I need a recommendation for a suitable GPU memtest...

Maybe memtestcl from the FAH community? Folding@home - DownloadUtils

Other than that, most folks would just use whatever GPU stress testing program they could get their hands on (make sure you monitor gpu usage to ensure that the drivers aren't throttling it back) and RMA based on general failure rather than discriminating between GPU/Mem as being bad.

I use Video Memory stress Test for Clean Environment (vmtce)
VMTCE | Free System Administration software downloads at SourceForge.net

You can run it in Windows or boot directly into the .iso. I use the latter with YUMI on a bootable usb drive with other diagnostic tools.

Although I find using furmark and running the benchmark to check for artifacting does the job much better and quicker.