In the final moments of the Shipyard level, Rainbow is tasked to run a gauntlet of terrorists lying in ambush to reach a ticking time bomb with only a minute and thirty seconds to spare (the timer doesn't start until you reach a certain point in the level after you get the objective, but whatever).
Chucking grenades and dropping foes like nobody's business, the team finally makes it to the final room despite the loss of Eddie Price to a machine gun-toting tango. After an intense dash for cover followed by a brief and lethal firefight, three Rainbow team members stand victorious.
I completely blanked about what I had come there to do. I heard the beeps, saw the timer at ten seconds and realized that something was nearby, but the dots weren't connecting in my head. When I finally remembered the bomb, I only had six seconds left to deactivate it. I ran up to it and started disarming it. I wasn't even halfway done when it exploded, killing myself and all members of my team instantly.
Rainbow Six 3 on Xbox. The explosion was actually pretty neat since RS3 has extremely solid ragdoll physics, probably tied for the best I've seen with DE:HR. It's a shame that the underlying game is relatively bland in single player.