Ol' Buddy Ol' Pal

Ol' Buddy Ol' Pal is an achievement/trophy in Fallout: New Vegas.

Requirements
Successfully convince one of the eight companions (including ED-E, Craig Boone, Veronica Santangelo, Lily Bowen, Rex, Arcade Gannon, Raul Tejada, or Cass) to travel with you.

Bugs
This appears to only be triggered by the very first companion you recruit so, if achievements are disabled at that time, recruiting other companions later will not unlock it.