Cruise ship captain
Police detective
President of the USA
Vampire
Architect (the same one, several times)
Hit man
Melon farmer
Western gunfighter (at least two different ones)
Matt Dillon? (a shot in the dark, but he was an architect in There’s Something About Mary)
Nope, not Matt Dillon (and Dillon was a sleazy private eye in There’s Something About Mary)
Charles Bronson.
Oops, forgot to add one…
Jewel thief
Cleaner
Cop (at least twice)
Preacher
Harvey Keitel?
Winston “the Wolf” Wolfe in Pulp Fictioncould be considered a Cleaner.
He was the preacher in From Dusk To Dawn.
Det. Rocco Klein in Clockers, Police Commissioner Frank Starkey in The January Man
not sure about the jewel thief, though.
Right- he was a peace-loving achitect turned vigilante in the Death Wish movies, he was a hit man in The Mechanic, he was a gunfighter in both** The **Magnificent Seven and Once Upon a Time in the West, and he was a watermelon farmer battling the Mob in Mr. Majestyk.
Gardener
Chinese detective
Indian actor
Sleazy playwright
Okay, that’s Peter Sellers.
The Gardener’s Chance in Being There
The Chinese detective’s Sidney Wang in Murder By Death
The Indian actor’s Hrundi V. Bakshi in The Party
The Sleazy playwright may be Aldo Vanucci in After the Fox, but since that character’s also a film maker and, more imporantly, a master thief, you may have had another role in mind.
You are right about Sellers. Sellers also played the sleazy pedophile playwright Clare Quilty in Stanley Kubrick’s movie version of Lolita.
Army private
High school football coach
Hollywood screenwriter
Munitions factory worker
Commissioner of police
Navy supply ship captain
Songwriter
Weaver and amateur actor
Goldie Hawn?
Leslie Nielsen
The Poseidon Adventure
The Naked Gun
Scary Movie 3
Dracula: Dead and Loving It
Yes- Private Benjamin, Wildcats, Swing Shift and Best Friends.
You got it.
The only one I posted that’s still unsolved:
Gallant knight in armor
Ghost
High tech weapon designer
Old West sheriff
New one:
Executioner
College president
Attorney
Horse doctor
Correct.
The jewel thief was from Reservoir Dogs.
Oddly, I was thinking Bad Lieutenant and Thelma & Louise for the cop roles.
Actually, your username was the clue to the Cleaner. 
Another new one:
Empress
English music-hall singer
Scientist’s fiancee (more than one)
First daughter