Traps

In the first one, There is a way to defend against this after the knight take but the knight will be taken back and the king will be unsafe. 

The second one is a well known trap. A lot of people don't fall for it but it's still very useful.

the third one isn't much of a trap but black can't win the game because the F1, F2, F3, G3 and H3 squares are protected, the king can't cone close enough to the king. So as long as white keeps moving his/her king inside the box and don't move anything else, it is a drawn game.