One thing is interesting on a current rewatch...
Travolta's personality changes depending on what is going on very well
He starts the day in a good mood, going to Brett's apartment with Jules. Cracking jokes, etc
shyt goes south after they kill marvin, the shyt with the wolf, you see him getting fustrated as the day goes on, dealing with all that chaos. Then they go to the diner, get in a fukking standoff, and now he's fukkin tired of this shyt...he was about to kill honey bunny and ringo off GP. Then, he gets to Marcallus' bar, and immediately punks Butch
"i'm not your friend palooka...you heard me fine punchy
"
He leaves, gets the heroin, and gets high. Watch Travolta after that. He's kinda nodding off at the diner, he's barely paying attention, his communication changes, etc....he's literally acting high, and doing so well. If you've been around an opiate user who's 'managing' it well, he's doing it...probably better than Uma is portraying someone who does coke.
Mia ODs, he fukkin snaps back and sobers up immediately but is really tired of this shyt, desperate for this whole affair to end and threatens his dealer to help save mia. Honestly...Vincent Vega had a shytTY day
The next morning there isn't much to say about his acting other than his shocked look when butch shoots him...but shouts to Travolta for this performance which I never really appreciated. Its not as obvious since the movie isn't chronological.
he's not the MVP but he's a starter