I just found this list of 34 free first person shooter games on Metafilter, and it is good. This type of game is not for everyone, but if you fancy a little over the top, graphically rich, adrenaline pumping action then you could have fun with some of these. For those with a more sensitive disposition, may I recommend the altogether more sedate World of Padman from this list? Enjoy!
kak!!!!!!!!