The Whole Gang's Here
The eight companions you need for this achievement are: Arcade Gannon, Craig Boone, ED-E, Lily Bowen, Raul Tejada, Rex, Rose of Sharon Cassidy, and Veronica Santangelo. You must get all the companions in one game in order to get the achievement.
pc ps3 xbox360 This achievement may on occasion bug and instead of hiring all of the companions, all you need to do is hire 8 companions; even hiring the same companion in 8 playthroughs qualifies for this achievement. [verified]