"HEY VORTIGAUNTS! THERE'S THIS OBNOXIOUS ARSE IN A SUIT THAT'S MAKING ME DO ALL THIS! RING ANY BELLS?"
I always facepalmed at the fact that Gordon was unable to tell anyone about the Gman. The Vorts obviously know about him, but Gordon can't query them about it.
Here's another.
"God damn, I survived an explosion that tore a hole in spacetime, I was put in stasis in a pocket dimension for 20 years, I survived another, huger explosion that destroyed a city as well as tearing a hole in spacetime, I've killed more zombies, aliens, and cybernetically enhanced soldiers than anyone could count in a lifetime, and I carried a garden gnome twenty miles and launched it into space. And I can still see through these glasses."