I prefer to accentuate the positive, but here is an incomplete list of stuff I don’t like:

liars
spelling errors on city street signs
bad table manners
mean dogs
most cream-based sauces
dirty bathrooms
plastic bags
that squeaky sound my shell toes make
the republican party
blockbuster video
the crack in my windshield
disappointment
things that are sour
jaegermeister
litterbugs
split pea soup
the new townhouses in my neighborhood
driving in tunnels
toilet humor and/or discussion of bodily functions
birds as pets
cheesecake
perez hilton
squirrels
people that don’t like led zeppelin