A couple kinds,
a couple minor hardware modding- Made my case bright as hell with 2 12" cathode tubes.. drilled a hole in the back of my case for the cathode switch, put an old pIII socketed heatsink on my old geforce256 for fun a couple years back and overclocked it with glee...
software- A friend of mine and I once edited all cs maps from 1.5 and put monsters and items from half-life in it by using hammer, and we tried to make a mod but we couln't skin at the time so we just edited the enemy health, power, and location in single player halflife because we thought it was too easy on its hardest mode........ yep, those were the days

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Asus A8N SLI - Opteron 148 @ 2.8 under a Zalman 7000cu LED - XFX 7800GT oc'd - 1gb Kingston Hyper X pc3000 BH5 2-2-2 - OCZ ModStream 450watt - WD 36gb Raptor - WD 320gb Storage Drive - Antec Super LanBoy - NEC 3550A 16x DVD Burner
Accessories:
ViewSonic VA1912wb 19" 8ms Widescreen - Plantronics Audio 90 - Logitech Z-640 5.1 - Razer Diamondback Plasma LE on a Ratpadz GS
Linux Box:
Pending..