I think the hard core gamers still go for mice. Not just any mouse will do. It's gotta have excellent resolution. Check out this link URL: http://www.razerzone.com/.
Many of the top Quake 3 arena players uses the Razer Boomslang mouse. I would choose a USB mouse over a PS/2 also for more smoothness. The mouse is longer with slightly grippier buttons than a normal mouse. The mouse wheel also has 45 clicks per rotation which is more than double a normal mouse. All of this info is contained in the link.
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