Creeper

The creeper is the most iconic mob in the game. If you're unfamiliar with this, head over to the comics tab and check out the surplus of comics about the creeper. The creeper is a green, slow-moving, kamikaze mob, resembling the male genitalia, which awarded it the name "A Walking Penis".

The creeper was introduced in survival test, and is considered one of the hardest and scariest of mobs. If it gets within a square of you it lets off a "hHissSSS" sound and blows up. When trying to take it out, wait for it to get within your sword range, hit it, and go backwards. Successfully killing a creeper will result in it dropping 0-3 sulfur. Failure will result in an surrounding terrain being destroyed(do note that stone doesn't blow up), as well as taking away a huge chunk of your health. Sulfur aids you in making TNT, which means the only way to get TNT is to slay creepers.