First game of Warhammer 40k ever back in 2nd Ed. Lascannon hit my Eldar Dreadnought, critical damage, exposed the soulstone, caused everyone of my Psykers Heads to explode.
Another 2nd Ed Game. One shot to my Rhino, blew it up, caused it to flip over onto my other rhino, causing a pen hit and blowing it up flipping it over killing every model in both Rhinos including my command squad.
For those of you that don't know 2nd ed, 2 squads with rhinos was roughtly 80% of your points, btw it was the first shot of the game, I had not even picked up the dice. Only time I have been annialted on the first turn before I had a chance to move my models.