I don't really like the taste of eggs so I put a lot of stuff in the omelette:
I mix eggs with a little milk, salt, black pepper, crushed red pepper, and some other herbs (oregano, rosemary, etc). I will also add some onions and cilantro to the mix.
Folded inside the omelette will be any/all of the following:
-cheese (sliced american, parmesan, feta, provolone, mozzarella, cheddar, whatever)
-tomato
-bell peppers
-olives
-mushroom
-spinach
-onions
-green onions
.. i am sure it does taste really GOOD! gotta try this one 