There are many deep results (long-standing, famous, etc.) for which only one approach is known. Can you give examples of deep results, for which several genuinely different proofs have been found? With the example of the prime number theorem in mind, it would be interesting to know if these proofs are all considered equally hard, or some are significantly easier or, perhaps, even surprisingly easy.

Edit: I will narrow the definition of "depth" to the results which (a) occupy an important, if not central, place in a field, (b) are clearly attributable to an original paper (please cite).