I've never tried, but can you kill Yes Man? If so, what happens if you kill Yes Man, Colonel Moore, Caesar and Mr. House? That would render all possible alliances leading to an end story impossible . . . does the game give you a special message that you failed :facepalm: or does it just allow you to explore and never finish . . .

Nope, you cannot kill Yes Man, no matter how you try. If all else becomes locked off due to your choices in killing everyone else off, you can always do the independent route. The only way I could imagine destroying Yes Man would be via console command... and even then I am not certain it would work since he is set to respawn almost immediately upon his death.

yes man is just so HAPPY to help you even death wont stop him!

He says it's impossible to kill him unless you kill EVERY other securitron out there ( because he jumps from one another). Ask him something about killing him and he says something along those lines.

Um, I think that's Victor.

Victor only does that so long as Mr. House is alive; once he dies, Victor shuts down (along with a few other unique Securitrons) and is never seen again. Yes Man does that regardless of whether or not House is alive.