Swing Glitch

The swingset glitch (also called the Car Cannon) is one of the more famous, and humorous, glitches in Grand Theft Auto IV. It encompasses a certain swingset which is capable of catapulting the player or their vehicle through the air with considerable force.

Locations
There are said to be several "glitched" swing sets around Liberty City and Alderney, the most infamous of them being the swingsets in the playground in Firefly Projects, yet two are accessible to cars and vans, and the one in Tudor near the Globe Oil gas station. Most of these are easy to access, specifically the two listed above, so it leaves sufficient space to allow the player to maneuver a decent-sized vehicle into position, the most popular method of exploiting the glitch.

Description
If the player presses up against the swings in a vehicle it will often, with little to no warning, be flung an incredible distance through the air. It is not uncommon for flying vehicles to reach or even clear Outlook Park to the west, and Algonquin if done in Alderney. The end result of vehicular flight is almost always catastrophic body damage (often in a manner that is not easily achieved through normal crashes), although the engine will frequently still run. This enables the player to cruise away in their ruined vehicle.

The player risks being thrown out through the windshield upon launch, facing the vehicle towards the swing increases the likelihood of this happening. After being thrown out, the player may fall to their death. The likelihood of this is lessened if one is thrown to the east (where the player may land safely in water). However, it is nearly impossible for players to get launched through the windshield in multiplayer. It is recommended that the area of the vehicle containing the engine not touch the swing set, lest the engine catch fire.

The best swingset to use is the northern one, as using the southern one will almost always guarantee crashing into large apartment buildings. It is often also preferable to use the middle pole rather than the side ones. The Alderney swingset will usually result in you landing on the docks, but can also land you in the water or even in Algonquin.

As well as flinging vehicles, the swings have been known to hurl players, as well as unsuspecting pedestrians that hang from or brush against them. Although amusing, this will almost always result in their death, unless they are lucky enough to land in water.

To get the most distance, back the rear of the car up to the middle pole then reverse. When the swing catapults you, you should go the furthest you can go (e.g. East Hook, this is one of the furthest locations the vehicle can land in).

The swingset can be useful for escaping the police, provided the player survives the landing.

If you try this with a helicopter it will lead to losing its blades and then blowing up. This happens 9 out of 10 times actually.

Best vehicles
Most vehicles are capable of travelling some distance, but some will only yield good results infrequently. For example, the Ingot, Blista Compact, and Yankee can be launched as far as the Humboldt River under the right conditions, but such range is unpredictable and can be achieved only rarely. Other cars, such as the DF8-90, seem more responsive to the glitch and will give more regular results.

The vehicles that seem to give the maximum frequency of launch and distance of travel are as follows:
 * Turismo
 * Cabby
 * Declasse/Vapid Taxi
 * Habanero
 * Stallion
 * Merit
 * Minivan
 * Moonbeam
 * NOOSE Cruiser
 * Perennial
 * Police Patrol/Cruiser
 * Esperanto
 * Rebla
 * Hakumai
 * Comet
 * Presidente
 * Admiral
 * Dukes
 * PMP 600
 * Voodoo

It is possible, although difficult, to use the glitch on a motorcycle, although it is unwise to attempt this owing to the massive likelihood of being flung from the bike, often with fatal results. It is also possible to exploit the glitch on foot, usually by jumping and hanging from the swings' crossbars, although this again carries with it a large element of risk - often the player will simply be launched directly into the floor at tremendous speed (fatal), and even if the player does become airborne, unless they are fortunate enough to land in the sea they will slam into the pavement or road upon their return to earth (also fatal).

Very rarely, players have been known to survive getting thrown from the swingset, usually by means of putting a car (preferably not a brute) underneath the swingset bars and having a player climb on top of the car and jumping over the bar, if timed correctly the player will usually be thrown in whatever direction they were jumping, and in some rare cases; will freeze in midair, do the standing up animation while floating to the ground and retaining full health, other cases cause the player and sometimes the car to be destroyed.

Larger vehicles are generally not good for exploiting the swing glitch as their increased weight limits the distance they can be thrown. However, if a Bus, APC, Yankee or a Benson is used on the swingsets, the vehicle may be launched underground into Blue Hell, often spinning wildly and uncontrollably until it respawns randomly on a road, usually somewhere near the swings. A further, rare glitch that only can be done in Broker will cause the vehicle to disappear entirely, leaving the player stuck in the nearby jungle gym while in the driving position.

Rolled Over
The swing set can be used to obtain the "Rolled Over" achievement/trophy (a car must be rolled over 5 times in a row from one crash) as the swing set is capable of rolling a vehicle multiple times in mid-air, though it may take some time to achieve a suitably violent launch.

Trivia

 * When the glitch is attempted on an uninstalled game on a console (especially PS3), the console will freeze.
 * Rarely, the player's car may become invisible when they attempt to launch it, yet it can still be driven. The swingset can also vanish into thin air, as if it was never even there.
 * Occasionally, vehicles such as the Ambulance will become lodged so that the top bar of the swingset will clip through the vehicle.
 * Sometimes, if a car explodes upon driving into the swingset, the player can survive inside, and can exit the vehicle with full health.