If there's any one thing that cheaters will try to have it's a fairly high k:d - otherwise, what's the point?
You can use HLstatsX to help find people who have insane k:d ratios.
I sort the list by k:d with a minimum of 50 kills. I know I've had lots of times where I start out on a hot streak (especially as an engineer) and have a 10:1 k:d starting out, but it inevitably and sadly moves toward the mean in the end.
http://interrobang.hlstatsx.com/?mod...sc&minkills=50


