After you receive the invitation to The Fort from Vulpes (or Alerio if you've capped Vulpes), Caesar makes a speech when you first meet him listing the The Courier's accomplishments.

So, let's make a definitive list of what he says - mainly because it's fun to annoy the old baldy slaver (sorry Legion fans). I'm paraphrasing from memory here.

"A man almost kills you, so you track him halfway across the Mojave?"

"You waltz into the Lucky 38 like someone slipped a key under the mat?"

"You assassinate the head of the Chairmen, in his own casino, and get away with it?" (If you kill Benny in The Tops) "You walk into The Tops and send the head of the Chairmen running for his life?" (If Benny escapes)

"After you leave the Lucky 38, the Securitrons have new faces?" (upgrade them to Mk 2, either through House or Yes Man).

"And the coup de grace? Mr. House dies after you enter the Lucky 38." (Kill House).

If you've annoyed him;
"You're the courier whose caused so much trouble for my Legion, and yet you dare come before me?"

"My garrison at Nelson has been wiped out." (Kill the legionaries at Nelson completing Restoring Hope or by simply gunning them down).

"The Great Khans aren't exactly clamouring to fight for my Legion now." (break the alliance, or convince them to ally with the NCR? Can't quite recall)

"All my bribes to the Omertas ended up buying me...nothing." (foil the Omertas plans, capping Big Sal and Nero).

"Years of work placing a deep cover operative...wasted." (foil the monorail bomb plot and identify Curtis as the spy).

Surprisingly he hasn't a thing to say if Cottonwood Cove is wiped out, either manually or irradiated through part of Eye For An Eye.

Any I've missed? I've only completed We Are Legion with my pro-Legion character, but he didn't comment - are there pro-Legion comments he makes?

I dont know if there's one for killing Vulpes Inculta in Nipton

No, the only difference there is that Alerio contacts you and says you will be forgiven for crimes against the Legion, including the "death of the fearless Vulpes Inculta.". Also I think you lose the dialogue option to talk about Vulpes and the Frumentarii with Caesar.Oh, and you lose his quest The Finger of Suspicion.

well, then it looks like you got all comments there

he may also comment on certain ''crimes'' after you meet him for the first time, e.g. after I completed Restoring Hope he said something like ''You really thought I wouldn't find out about you helping the NCR take back Nelson?''

Caesar was one of my favorite characters to kill, mainly because you had to wipe out the enitre fort first.

Well i just went to talk to Caesar because of this thread and he complained that i allied the Kings with the NCR so now they can relocate their forces from Freeside to the dam.

I did that after I started working for him.....for some reason about 15 NCR troopers spawned and rushed Nelson, so after they killed all the Legion dudes outside I went to Piloti and took the final Restore hope mission. Then I went to Nelson, went into the barracks and got Dead Sea and his buds to chase me outside, where they were promptly gunned down by at least 10 NCR troopers ala Butch Cassidy and the Sundance Kid. Took the town without any Legion infamy at all. Caesar was pretty mad about it, too.

Vulpes Inculta also has a different initial greeting at Nipton depending on how far along the game is and what you have done. I decided to bypass him and his party this playthrough after speaking with boxcars, I didn't feel up to fighting five legionaries so soon after getting shot in the head. I thought he'd get bored and leave eventually but much later in the game I returned and he was still there. Then I went and had a chat with him and surprisingly he said something different.