Hell, yeah. Diablo 2 multiplayer was some of the most fun I have ever had.

Also, seeing 3d gibby chunks in the Quake beta. Awesome sauce.

How about TFC with cl_gibcount set to 9999?

Ah, those were fun times. You headshot somebody as a sniper and suddenly they explode into a couple hundred gibs, usually of the same 4 body parts.

right at the end of HL2 when the wierd old guys comes and stops time. most awesome thing ever. especially considering it wasn't even a cutscene

It was also cool to turn on noclip and fly around the map to find Dr. Breen somewhere in the map where he is giving his speeches in real time.

Garry's mod and the things people can do with it are cool. I've read a whole comic series made possible by Garry's mod as well as some humurous videos (Full Life Consequences and The Idiots of Garry's Mod).

Jail defense in Half-Life 2.

learning to soviet heavy tank rush back on Red Alert 1.

OH OH! I got a winner. Final cinematic of Starcraft. You know the one I'm talking about. The one that has made Tassadar THE badass of all games, untouchable by any character, or any alliance of any number of game characters (yes that includes kratos, link, MC, Samus alliance). He is my god, 'nuff said.

When I leveled to 60 in original WoW. God that moment pwned.
Heck, the whole pre-bc WoW kicked ass.

The countless Terran vs Protoss games I played against my brother. The evolution of our battles was great. At first, we didn't know what we were doing, then I discovered how to lay multiple mines at once with vultures, crippling his zealots. Then I learned how to reaver drop effectively. Then I learned to build missile turrets early. Etc...

God I love that game!

the moment i was able to preload half-life 2 to my computer... it was awesome because i had all the files but i couldn't play it yet