I like to keep it simple with cheese and tomato-- and sometimes with a tiny bit of green chili if I want to make it interesting.

But really, my favorite egg/omelette is the tortilla espanola in Spain with eggs, potato and onion cooked in lots of olive oil (puffs up like a circular cake if done right) and served with french bread! Heaven!

Saute together onions, green pepper, diced tomato, sliced mushrooms, diced ham. Put this mix atop the omelette, cover with cheese, then fold. :p

Tomato
Ham
Bacon
Sausage
Mushroom
Bell Peppers
Cheddar Cheese

Topped with Avocado and Salsa

Fresh porcini mushrooms (known as cèpes here in France), chopped chives, with some wafer thin San Daniele prosciutto added at the last minute (it's important not to let the San Daniele cook).