That’s complicated by the fact that the Black Knight is just John Cleese (largely, actually amputees played him after the various amputations). I didn’t specify in the OP but that seems a bit of a cop out. If it does count then the top ten is all from Monty Python! Literally from the top of my head I can name…
Anarchist Peasant (“watery bints distributing swords is no basis for a system of government”)
Grammar Nazi Centurion (“Romans they go the house?”)
Stoned Pharisee (“even if they do say Jehovah!”)
Oh, stewardess? I speak jive.
No doubt- that would be A Bride Too Far.
For the “most influential” minor role, it’s got to be the Imperial Officer, right at the start of the original Star Wars, who tells his subordinate to hold fire, rather than blow up the escape pod that held R2D2. With one shot, the entire fate of the Rebellion and the Galactic Empire would have been completely changed. The entire plot of six movies and a lot of TV would have collapsed.
Though I meant culturally influential not influential in the plot
Though the star wars answer is pretty obvious (I would not include Boba Fett personally as between the Empire strikes back and return of the Jedi he has quite a bit of screen time, even if he doesn’t say much). Surely it has to be Greebo? He’s on screen for what 30 seconds, has like three lines, and you literally see people wearing t-shirts referencing his character 45 years after the film came out.
This man had a walk-on part as a sailor in Since You Went Away (1944) and instantly became an American heartthrob. He went to to have a long acting career in theatre, radio, TV, and motion pictures.
Suzanne Somers in American Graffiti as The Blonde.
Oh yeah that’s a good one. Massively influential (the odds are any salesman you know will have that speech memorized)
How about Trench,Sylvia Trench
Without her introduction, would we have ever got Bond’s catchphrase?
Another Princess Bride character: Miracle Max.
Sean Connery shows up at the end of Robin Hood, Prince of Thieves and almost single-handedly saves the day.
Hey, it’s Enrico Pallazzo!
Alfonso Bedoya:
You could say “Dennis”.
Mickey Rourke in “Body Heat”.
Jack Nicholson in “Reds”.
Robert Strauss in “Stalag 17”.
Most influential? Easy: Samuel L. Jackson, Iron Man. His post-credits cameo basically launched the MCU.
From the same (tremendous) movie, don’t forget,“Our precious bodily fluids”.
Banjo boy from Deliverance
More memorable target for Harrison Ford: Greedo, or That Swordsman Who Never Had A Chance?
The classic one for me is always Wilford Brimley in Absense of Malice. In a sense it might be arguable how minor his role is, but he is introduced basically at the denouement of the film and probably has less than ten minutes of screen time. But he dominates it.
