Projectile physics were one of my favorite points (besides the open environment). You had to be aware of your own motion vector if you wanted to accurately place a shot with most weapons. Sadly, later installments (T:V, I'm looking at you) never quite had that same feeling. That was probably part of what made it relatively unfriendly to newbies from other shooters, but I felt it made the game a bit more intense and required a bit more focus rather than strictly mindless button-mashing.