If you are bored of doing push ups and want to do something that's going to challenge you, try this:
Pike Push Ups:
Here's how it works:
Begin in push-up position, with hands wide facing the middle (fingers pointing towards each other). Bend at waist, lifting hips up and coming onto toes so body forms upside-down “V”, pike position. Bend elbows to lower head toward hands. Press back up.
These are really hard! I tried them for the first time a few weeks ago and could only do 5 before losing proper form and feeling like my arms were made of jelly. I highly recommend that you try this out.