Personally, I saw the 'evil Blair' ending first, but only because my friend Sean was at the end of the game when I walked in. ~LOL~
The first ending I earned was also that one, but then I tried ejecting in the 'Roast the Vesuvius' mission (sans F-Pak), and I saw the cool 'Traitor' ending.
And I didn't even know about the 'being fired' ending. I'll have to check it out!
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Maestro: "Lighten up Spyder! We're not gonna die! We're gonna WIN!!"
Zero: "Hey, Maestro... Uhh... If you DIE, can we pick through your stuff before we head back to Sol?"
Maestro: "You can burn in Hell."