I have a German keyboard layout, so it may differ for you if you use a different one. When you click on the keyboard icon (square with your keyboard's nationality written to it) in the panel and chose to view the key mapping (real translation might differ), you see which key corresponds with which character.
On my keyboard layout, the letter keys have special symbols assigned to them in 3rd (with AltGr, lower right corner) or 4th (with Shift+AltGr, top right corner) level. If you now look at those keys, you'll find a Ω on the Q key in its 4th level.
That means in my case, I have to press Shift+AltGr+Q to easily and quickly type the Ω-sign.
Explore your own keyboard layout and find all the hidden gems! ;D