I'll make two lists for you, one for games that hold a special place in my heart.. and another one of my favorite games of all time.. because they are two different lists.
Special Games to me (that most prob dont care about, nor would find fun these days)
1. Movie Monsters for Commodore 64
2. Knight Games for Commodore 64
3. Rampage (the 80s arcade game)
4. Golden Axe (80s arcade game)
5. All the old Sierra games (Kings Quest, Space Quest, Quest for Glory/Heros Quest)
My favorite games (this list constantly changes unlike the first)
1. HL2/CSS
2. All the PopCap games (check popcap.com, some small, exceptional games.. my favorites are Insaniqurium, Zuma and Bookworm)
3. Doom3 (sorry I just like this one.. it may be old school but I was a big fan of Wolfenstein 3D and the original Doom.. so I just like it)
4. Savage (a really cool game that is free now! heres the link
http://home.ripway.com/2005-1/248022/Savage.html)
5. SWAT4/Splinter Cell Chaos Theory
Hope I helped ya out VIAN!