I've sample most of the beers listed in this thread. But one stands out as the worst I've ever had. Wiedemanns. Watered down with almost no flavor.
Used to get a case of returnable bottles for about $7. It tasted awful, but I was on a student's budget and the price couldn't be beat. I drank a lot of this swill.
They also had a "bock" that had a bit more flavor, but it gave you beer farts.