Alyx is perhaps the first crush of many young gamers. Appearing in Half-Life 2 (and the subsequent episodes), Alyx has fought against the alien Combine in an effort to save humanity. Mixing it up with a skill-set that includes: CQC, pistol and shotgun use, coming back from the dead, and causing dimensional tears alongside Gordon Freeman, Alyx is a force to be reckoned with.
Among Alyx's kill-count are a number of headcrab zombies, antlion guardians, and presumably larger Combine war machines. Paired up with her personal pet-project (I'm really sorry for the puns today, guys), she is the ultimate survivor in the Half-Life universe. Her intelligence, reputation, and general bad-assery earn Alyx Vance the spot of #8 on this list.