Okay, so simply for fun I thought I'd be a naughty girl this time around. Have been working with Caesar, healed him, even killed the President. Now Boone has "lost all respect" for me. (Goodness, I wonder why...?) I've completed the game, yet returned to a Save point (just after killing the President). Boone now rejects me. Question: Can I ever regain him as a companion or are we done...? Thanks, gang...!

nope, that train has moved on. Naughty girl u shoulda the big Ncr symbol on his head for everyone to see.

Get your NCR rep to accepted and CL below accepted. That should work, also try wearing NCR faction armor near him.

You're done.

Boone has no tolerance for anti-NCR and/or pro Legion actions.
Veronica has no tolerance for anti-BoS actions.
Arcade Gannon has no tolerance for actions he deems inappropriate if you can't provide good, reasonable justification for doing it. (sometimes to the point where he'll leave IMMEDIATELY if your argument svcks)
Cass has no tolerance for a bad karma character.

She is. As long as you comete her mission first and dont shoot first in the quest, ur ok.

That reminds me, anyone got any advice on a cowboy taking down 3 paladins wearing light armor?

I wouldn't be so sure, as I've heard conflicting reports on it. If you simply don't take her along when you go to kill off the BoS, she's fine. If you do though, I've heard conflicting reports, with some people saying she's fine with the self-destruct sequence but NOT with manually murdering everyone, or that you absolutely need Idolized rep (difficult to get with the BoS) to avoid her leaving.

And if you're talking about the firing squad that hates what Veronica's trying to do....I've yet to have a character survive that the first try, bar my pacifists who talked their way out. If you can really only rely on guns (no unarmed or melee option) then take cover and aim for their guns first-thing, THEN worry about finishing the kill.