Battletoads is a great scrolling beat-em-up for up 3 players, or for 1 player only if you have no friends.
There are 3 toads to choose from Ritz, Dimple and Shaking Stevens. The best part about the game is that each toad has multiple devastating attacks, which involves parts of their body becoming very large. This can often cause fatalities such as decapitation. On Stage 3 it even has a rat having a poo in a toilet. After a few grunts of constipation the diarrhoea sounds are heard and the rat even has the courtesy to flush when he's finished.
I'm being serious, these are things that really happen in the game. Except for all the names though, I just made them up.