Deep down, every physicist knows that, if the experiment he was a part of went horribly wrong and released a horde of aliens, he would be able to master terrestial and alien weapons and fight his way out, saving the world(?) in the process.
Who knows, he might even get to make out with Alyx.
Thanks Matt for giving me a copy of Half-Life 2. I started playing it tonight. Man, those flying circle-saws are irritating…