Special Vehicles in GTA IV

Unique vehicles are not something new to GTA. Unique vehicles can sometimes be very hard to get, as they are either mission related or they just appear as a one-time-only.

Warning: unique colored vehicles will be resprayed to normal colors upon repair, you will never be able to revert back to the unique color in Pay 'n' Spray.

Many of Stevie's (if not all) car theft's are also very unique.

Cars

Roman's Taxi

The Roman's Taxi is a Black Esperanto with emergency light. This may be the first special car you can get. It's easy to get, but after Romans depot is burned down, the car is no longer available as it gets replaced by a fleet of gray Cavalcades.

Merit

In the mission First Date you are given a lustered silver Merit. You can save it when the mission is completed.

Laundromat

The Laundromat is a laundry van that only appears in two missions. The most easiest way to obtain it will the mission Hung Out to Dry. It can be found in the back of the laundromat, stealing it, however, will result in mission failure.
It's second appearance is in the mission Meltdown, where it is used in a scripted sequence. This one can also be stolen, and if you are good at driving a van in a chase, you can complete the mission without failing it.

Marbelle

A Sky blue Marbelle appears in the first cutscene during the mission Clean Getaway. Later in the story, when Vladimir tries to escape from Niko, he drives the sky blue Marbelle again in the mission Uncle Vlad. When he reaches the Humboldt River, he leaves the car and makes a run for it. This is the chance to take it and keep it.

Blista Compact

A pure white Blista Compact can be stolen in the mission Clean Getaway. Also this is the modified variant of the Blista Compact which is normally red. To keep the car, drive it to your safehouse parking space and then commit suicide, which will result in mission failure, but the car will get stored anyway.

Ruiner

Ivan Bytchkov owns a black and yellow Ruiner which can stolen during the mission Ivan The Not So Terrible. When Ivan crashes his car into a truck, he will try to escape on foot - don't go after him just yet though. First, take the car to the end of the block to the south and park it where your will eventually get to Ivan.

Virgo

A red and black Virgo appears in the mission Concrete Jungle. It can be taken and saved at your safehouse.

Feltzer

Gracie Ancelotti owns a special pink Feltzer that can be acquired after the mission I'll Take Her.... However, you must be quick to get it, otherwise, the driver will drive off and disappear.

Coquette

A lustered black Coquette appears in the mission Payback. To obtain it, simply follow the goons until they stop at the building.

Infernus

You have to steal an Infernus for Stevie. It is a unique gold color. Like many of Stevies cars, they re-spawn after a while. It is located at Montauk Ave. Downtown, Broker, but only if you got a text message from Stevie.
Also, after you completed the mission Buoys Ahoy, Bernie Crane will call you to collect Bryce Dawkins' special orange Infernus as a gift. Like many other cars, the Infernus comes in two different variants (with and without Spoilers).

Super GT

One uniquely colored Super GT appears in the mission Union Drive for Bernie Crane, driven by Dimitri Rascolov's henchmen. The paintjob is black with a blue sheen, a paint job not seen anywhere else in the game.
Another uniquely colored Banshee appears in a Most Wanted mission in which you are after a drug trafficker named Darren Covey. You find him and the five friends of his whom you must kill also on the second floor of a parking garage in Purgatory, with a few cars around them. One of these cars is a Super GT whose paint job resembles a mixture of McReary Mob green and sky blue not found anywhere else in the game.
What may be a third unique (if someone could please confirm the rarity of the paint job by using the Super GT cheat code, which is 227-555-0168, and going through all of the colors until one of the colors repeats, while checking to match sure that none of them match up exactly with this Super GT, that would be helpful) Super GT appears in one of Stevie's Car Thefts. It is in front of the 69 Exchange in Chinatown, Algonquin.

Banshee

There are several unique Banshee's in GTA IV.

A blue Banshee with grayer color than normal and a white stripe is requested by Brucie for his Exotic Exports.
A Banshee with yellow stripe and a orange paintjob is requested by Stevie.
In the mission Meltdown for Ray Boccino, the car chase begins with the player driving a Banshee. This Banshee has a unique grey-a-bluish-green-stripe paintjob.

Romero

A Romero appears in the mission Undertaker. This is the only time it appears in the entire game. To obtain it, steal it when the mission is done, but you have to be fast and alert, otherwise the driver will drive away and disappear. The Romero will also appear on the street, but only if you are driving one at the time.

DF8-90

A lustered black/silver DF8-90 appears in the Mission Crime and Punishment. It's in the driveway at Mikhail Faustin's house. You can save it if you want to. It comes in three variants.

Comet

A bright yellow Comet is given to player as a racing car in the mission No. 1. After completing the mission, Brucie allows the player to keep the Comet.
A Comet with a unique mauve paint job is requested by Stevie for one of his car thefts.

Patriot

A bright yellow Patriot can be acquired anytime after the mission Blow Your Cover for Playboy X but before his death. It will be parked in one of the RESIDENT PARKING ONLY spots outside his loft. To save it, simply drive it out of the car saving spot and drive it back in.
Two lustered silver Patriots appear in the mission Photo Shoot.
As part of Stevie's Car Thefts, there is a unique gold/orange Patriot with US flags on the sides.

Sultan

A unique blue Sultan is wanted by Stevie. You can take it and save it. A new one will respawn.

PMP 600

In the mission Museum Piece, there are three pure white PMP 600 "Sports" parked on the northern side of the museum. These PMP 600 "Sports" variant normally comes in complete black.

Bikes

Hellfury

In the mission Ruff Rider, there is a rich red Hellfury that can be obtained after you kill the enemy. Normal Hellfurys have a metallic red, but this one is a glossy red with no metallic added to it. After you kill Jayvon, the mission is completed, so you can take and park it at your safehouse.

Aircraft

Maverick

There are three unique variants of the Maverick:

One in the missions Dust Off and Paper Trail. In Dust Off, this requires a mission failure to obtain the chopper. It's recommended to save it in Paper Trail, because you can fly it to your safehouse after you beat the mission.

Another one appears in Babysitting. It is solid black with no white stripes on the top of the body. You need to capsize Derrick's boat, and after it starts flying away, ram it into a building, and then push it to your safehouse after it hits the ground.

Note: There can't be anyone in the chopper after it crashes. Otherwise, it won't save.

Another one appears in A Revenger's Tragedy ("Deal" ending), where Dimitri flies it. After you crash on Happiness Island, steal the chopper and fly it to your safehouse.