10. Gordan is BEAST
9.Barney isnt in the second expansion pack
8.Strider battles are EPIC
7.the combine look really cool
4.you single-handedly take down whole armies
3.Alyx Vance is HOT
2.Vortiguants are your allies and instantly kill everything except antlion guards and striders
1.It brought about the greatest editing program known to man: Gmod!