On my “good” characters, I always help out the small towns and kill off the NCR/Legion/House as quickly as possible. My character doesn’t need to rely on bureaucracies to get stuff done. I never end up using Boone because I hate the NCR too much (and he steals my kills), but I will befriend the Legion temporarily for the ridiculous amounts of ammo they give you.
On my “bad” characters, only the Vendortron, my followers, and Yes Man remain standing at the end of the game. The Legion get to live awhile, though.
If you go into console and 'tcl' (toggle collisions) you can get into the Vendortron booth and kill him too. :)