I’m working on software that has to give directions like Tom-Tom and I got to thinking it might be fun to have celebrity voices do the directions.
William Shatner: TURN. LEFT. HERE.
Samuel L. Jackson: I have had it with these mother fucking right turns on this mother fucking road. Make a mother fucking left here.
Marlon Brando: I’m going to give you directions you can’t refuse. Turn left here.
Gollum: It turns left here, precious, yesss…
Robert de Niro: You turnin’ right here? Are you turnin’ right here? You must be turnin’ right here, 'cause there ain’t no other way to turn.
Miss Piggy: Vous should turn right now, s’il vous plait. I said, turn right. Right! HIII-YA!
I’d totally buy the Miss Piggy version of this.
Yakov Smirnoff: In Soviet Russia, car drives you!
Actually, you can already download various voices for your Tom Tom. Most of them are just funny, non-celebrity voices, but you can select John Cleese if you’d like. 
How about a Bush voice that only lets you turn left, a Ted Kennedy voice that only turns left, and a Hillary voice that straddles the middle line?
HAL: Left turn, Dave.
Locutus of Borg; Turning is irrelavent, you will become one with the Borg
Dirty Harry; Turn left, here punk, go ahead, make my day
Sledge Hammer; turn right here, trust me, I know what I’m doing
Generic New England “Yankee” voice; Well, you can’t get theah from Heah…
Caprica Six; I know God’s plan for you, He wants you to turn right, here
Jason Voorhees; …
Garrison Keillor did a Bush spoof like this where it only gives you directions to “stay the course”…off the road, down a ditch, and into a house.
Rachael Ray- You make a RTRH, that’s a Right Turn Right Here,then go straight for less than 30 minutes and make a left turn at the GB, thats’s Garbage Bowl,then pull in at the stoup. Dee-lish!
Of course there’s the one that does Clint Eastwood as Philo Beddoe from “Every Which Way But Loose”:
“Right turn, Clyde.” (Requires optional passenger side orangutan.)
Someone who has enough of a sense of humor about things that I can imagine him recording the necessary sound samples for this would be Christopher Walken. And (like Shatner), it would even work with the slightly unnatural rhythm of the speech synthesis (at least, the synthesis in my Honda).
Although I’m not sure if having Christopher Walken guide me places would be awesome or disturbing.
Another one that would actually be cool would be James Earl Jones.
What happens when you try to drive near Chappaquiddick?
I recall a Reader’s Digest article poking fun at the Tom Tom pointing out that alongside John Cleese, Mr. T is also a real available celebrity voice. That might be interesting. “Turn left, FOOL!”
Maybe the voice of the guy who played Buffalo Bill in Silence of the Lambs: It turns left here or it gets the hose.