Pretty much any American macro lager, including Busch, Bud, Miller, Natural, etc. Unfortunately this stuff dominates the American beer market, giving the many finer brews also called 'beer' a bad name.
Pabst Blue Ribbon, Rolling Rock, and Coors are three generally recognized exceptions, each having a devoted following of discerning tasters despite their budget pricing. Keystone Light also has a devoted fanbase.
One easy way to judge whether a beer is bad or not is by the color of its can. the so called "silver and blues" are generally the bad beers. ie beast, natty, busch etc...
Don't be fooled into believing a beer is necessarily good if it is imported. Some of the overpriced, well-marketed "Euro" beers (e.g. Heineken or Stella Artois) are just as bad as the American macros, especially when they get skunked.
Sierra Nevada is terrible excellent though overrated. Try the "Pale Ale", you won't regret it.
And in case you are pretentious enough/actually enjoy having a good beer, try one of the Belgian offers that are usually available at Cole ave. and even spring street: Hoegaarden Witbier (white beer) 5%alc. Blanche de Bruges (white beer) Duvel (golden ale, absolutely amazing) 10%alc. Grimbergen Tripple (abbey/trappist ale) Lindeman's Lambic ale (flavored with cherries, peaches, etc.)
I thought this was supposed to be the "bad beer" section (?!?) People will be misled.
If you hate the Belgians, here are some other great brews (available at Spring st.): Samuel Smith - the whole range: Oatmeal Stout, Imperial Stout, Taddy Porter, Pale Ale, Nut Brown Ale, Winter Welcome Ale. Unibroue Le Fin du Monde Celebrator Doppelbock Stone Imperial Stout