I always thought there were two from "back in the day" that were pretty awful....Red White & Blue and Buckhorn (from Pabst and Hamms respectively). Milwaukee's best is another that I always considered nasty, but which still survives. And for some reason, I could never get into Miller Lite, although I like MGD and MGD lite (at least for big-mass marketed stuff).

Three that were trashed here earlier, I always thought were actually pretty good....

Watney's Red Barrel....nothing special in the bottled version but a great draft. I was really sad to see them go under.

Stag...before it got "dumbed down", this had a unique, crisp "dryness" that I liked. A very flavorful "blue collar" brew.

Carling Black Label....A little on the sweet side, but usually very drinkable.
(Not to be confused with Carling Red Cap, which was truly great stuff...especially the Canadian version).