Leonardo diCaprio’s South African “accent” in Blood Diamond.
Sounded like the director just told him to say “Huh?” after each sentence.
Were their Australian accents any better, Bruce? :dubious: 
I love the character of Pavel Chekov, but Walter Koenig himself has admitted he didn’t know what a Russian accent sounded like when he auditioned for the part. All he knew was that his grandparents (IIRC), who were from Russia, couldn’t pronounce “w,” so “very” came out “wery.”
After having lived in Russia for some time, I can tell you that Steve Martin’s “wild and crazy guy” comes the closest to a Russian male speaking English that I’ve ever heard. (And yes, I know he’s supposed to be Czech instead of Russian. Makes no difference.)
For that matter, I’ve had real Scots tell me that James Doohan’s Montgomery Scott accent was in no way authentic, though he claimed to have modeled it after a RCAF bunkmate who was from Aberdeen. On the other hand, I’ve also heard that someone (Gene Roddenberry or James Goldstone, maybe?) told him to tone it down a bit because they couldn’t understand what he was saying on film.
Well, but you see that’s the issue, a authentic Scots accent is such that we couldn’t understand what they was saying on film.
I lived in Scotland for four months and didn’t have any trouble understanding accents. I never journeyed north of Inverness, though. 
It’s easier in person than on film.
In college our skydiving club brought some students to the DZ (this was in the Midwest). One of them was from Scotland.
During the lunch break I had a conversation something like this with the owner:
Owner: I’m a little worried about that one guy, I think we’ve got a language problem.
Me: It’s OK, he’s Scottish.
Owner: (blank stare)
Me: They speak English.
Owner: (looks doubtfully at me)
Me: Really. It’s just an accent.
Gary Oldman says he can no longer speak with a normal English accent without some coaching.
To be fair, Cote de Pablo is Chilean.
Have you heard the Scottish accent James Mason used in Journey to the Center of the Earth?
I’m curious what you think of John Malkovich’s accent in Rounders?
Years ago I saw a comedic skit portraying a Star Trek in which every character spoke with an unintelligible Scottish brogue. Finally found it again. 
On the flip side, Matt Damon’s Afrikaner accent in Invictus was pretty good - and Morgan Freeman’s portrayal in the same movie of Mandela’s accent was pretty bad.
I’ll watch it when I find the time and let you know! 
In an episode of Dragnet, titled “Joyriders,” stock actor Peggy Webber uses a vague Southern accent. In none of the other episodes she appears in does she speak with an accent, even one in which her character lives on Central Park West in New York City. I was not impressed with her Southern accent–or with Virginia Gregg’s in the episode about Gypsy bunco artists, or Julie Bennett’s in an episode about a thief who gets into elderly people’s homes and steals money from them (at the end she speaks without the Southern accent, so the viewer can tell it’s affected.)