oh, I thought you meant manufacturers
one big thing about gamers: let people customise their systems. gamers are more often than not, very picky about their hardware
for gaming, use Athlon 64's. lots of gamers like them, and they are a good processor to use. you should also use some Intel's, not the 600 series or later, because Intel really screwed up on them. use the 500 series socket 775's
give them a choice of video cards between ATI and Nvidia, there are a lot of people that like ATI, and a lot that like Nvidia.
use the 6800's, X800's, 6600's, X700's, don't use X600's
motherboards:
use Abit, DFI and Gigabyte
DFI for really high performance
Abit for high performance at low cost
Gigabyte for those with less money and not into overclocking
RAM: give them a choice of G.Skill (high end) and OCZ (not quite as good, but less $$)
cases are a big selling point, you will probabbly want to have a big range of cases. Lian-Li, Thermaltake, Antec and Raidmax are good
