Original AvP is much better than the sequel, so if you haven't played it, go get it NOW!
http://compare.ebay.co.uk/like/320932703835?var=lv<yp=AllFixedPriceItemTypes&var=sbar&cbt=y
I've never been as scared (playing games that is) as when playing the Marine campaign.
NOLF I&II are indeed great games and you should definitely get them.
ww.magisterrex.com/proddetail.asp?prod=
http://compare.ebay.co.uk/like/260975386346?var=lv<yp=AllFixedPriceItemTypes&var=sbar&cbt=y
If you liked Doom, Doom 2 or Quake at all, you have to play Painkiller. It's awesome but strictly as a fast strafe shooter:
http://www.gog.com/en/gamecard/painkiller
Original Rainbow Six is still the best thinking persons "shooter":
http://www.amazon.com/Tom-Clancys-Rainbow-Six-Pc/dp/B00000DMAH
Only the first two sequels are worth playing, all others are ****.
Couple it with SWAT 4, where you have to follow police procedure to the T:
http://www.amazon.com/SWAT-4-Gold-Pc/dp/B000EDVRUA/ref=sr_1_1?s=videogames&ie=UTF8&qid=1341337295&sr=1-1&keywords=swat+4
All the Ghost Recon games are simple, ****ty and easy. Well, the original was fairly challenging but the sequels, especially the latest, aren't. Borderlands is ****. HL2 is good for one playthrough. Bulletstorm is ****. Far Cry and Crysis have their moments but do avoid the sequels which are awful.
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As for F1&F2 clones, have you played Arcanum? It's steampunk, not post-apoc, but very, very good.