Coors Light. The yanks may disagree, but I thought it was absolutely terrible. Just tasted...watery and ricey. Horrible.
Coors light has no taste. No taste is a lot better than rank taste.
I think I would have to go with a tie between Olde English 800 which could make you hurl after a 40 even if it wasn't for the 8% ABV, and Pearl Beer which had the ad campaign of the blue collar middle age guy in work clothes stating: "Pearl, it's a good beer, a good Drinking Beer" which loosely translated to "it might taste like ass, but when you're out to get hammered this won't cost you much and will get the job done."