Give me classic Doom 1/2.
I played doom for 7 years, alot of it was because of the maps I could get and build (go DEU 5.2! and dehacked for modifying the binary). It was also the first game that my friends and I played at lans, came over with our 486 computers, 10base2 BNC network cards, built out little IPX networks and had a blast (except one time I forgot the terminator so I had to bike home to grab it :S)







