Scissors are the other big one; most of them are designed so that when to try to use them with your left hand, you end up pushing the blades apart slightly so they don't cut as well (or at all).

With that being said, self-deprecating jokes about how left-handedness is an affront to God are definitely a prominent feature of lefty culture.

(Edit: I guess formal place-setting is another area of society that assumes right-handedness, as well as restaurants that pack people close enough together that everyone needs to use the same hands to avoid elbowing each other.)