Bleh, what a boring thread. Just state a game I loved to play?
No thanks.
I'll explain one of the best moments I've had in gaming (it's not "the" best but certainly in the top 50).
I played Counter-Strike Source and I was checking out servers with custom maps to them.
Then I joined in one server, it was dark, gloomy, a graveyard setting, and I saw a SWAT guy run past me and I shot him.
Well, the entire server lost their [censored] and told me to cut it the [censored] out.
Confused, I started looking around for stuff when I found this catatomb.
It was really... Really dark.. But I descended, only to have 5 zombies rush towards me and tear me apart.
The music was overwhelming as were the sound effects and zombie groans and moans.
I screamed in terror and when I was finally dead I sat there. Shocked.
And... Well.. It was freaking AWESOME!!!

Best zombie mod/game ever!
It was SOO much fun to play through.
Both teams start at two random locations then one player is singled out to start as a main zombie with 5000 health.
That zombie needs to hit you "once" and you become a zombie as well.
Now the zombies need to use tactics to get close to the humans and the humans need to run for their lifes.
Definitely one of the greatest moments I've had.
It's rare for me to get that scared in a video game, especially one as ugly as Counter-Strike.
So that moment was fantastic for me.