NoFrag

Another cool thing was the improved engine. Randy Pitchford said you can't actually call it the Half-Life engine any more, so much has been done to it

The walls now reflect the bullets

There are a total of 160 different models in the game. Each with a different face, in fact, it was actually difficult for Gearbox to find that many different faces so they had to ask people like the Pizza-boy and mail delivery man to "borrow" theirs

Of course the models also look more realistic, no more yellow guys running around (not that I don't like the leet guy, but realism rocks :))