" Red Faction Guirreiala(damn spelling) "

Fallout 3 by far has had the most powerful and impressive explosions I've ever seen in a game. What really sells it is how much of an impact the explosions create. It's like you really feel that blast, and it hits you so hard. In most games, explosions aren't very lethal, so when a car is on fire, usually you just step back a couple feet. In Fallout 3, YOU BETTER RUNNN!!! Plus explosions often have a nice trigger effect and set off more explosions, increasing the level of pure awesomeness. Heck man. Fallout 3 gets my vote already and I've never used a mini nuke yet and I've never blown up Megaton.

This thread needs less words and more pictures.
 

The coolest explosion, like the one that made me go "HOT DAMN, SON!" was the nuke in Call of Duty 4.

COD4 the nuke explosion was awesome and the aftermath and crawling along as you die.

" Most unique and LARGE explosions I can remember back in the day came from Starfox 64."

Red Faction: Guerilla, Mercenaries 2, Company Of Heroes, GTA IV, Crackdown...

Black?

I really liked GTA IV's 'splosions,.

Mercs isn't such a great game, but it has fucking awesome explosions. 

" The nuke that goes off in CoD4. "

The explosions in Bad Company 2 are indeed really nice. Watching choppers bone themselves into walls and then exploding in a blaze of glory is just breathtaking. Also, I always thought the fire and explosion effects in Borderlands were pretty:

Lost Planet has some really cool ones, and they're quite frequent.

" Lost Planet or GTA IV or Bad Company "

GTA IV and Half Life 2 because most explosion-related deaths are from flying debris. Physics make the threat of explosions realistic in that regard.