Unique Stunt Jumps
Every GTA game since Grand Theft Auto III has Unique Stunt Jumps, named Unique Jumps in the GTA III Era, and later renamed Stunt Jumps in Grand Theft Auto IV. The game tracks these for your stats, and completing all is usually required for 100% completion. Each unique jump has pre-defined takeoff and landing areas; miss either, and the jump is incomplete. If your vehicle hits the takeoff area in more-or-less the right direction, the game switches to a slow-motion cutscene panoramic view as your vehicle launches from the takeoff area. Upon landing, indication of success is given, while an unsuccessful jump will receive no message. Some jumps require high speed, thus are only feasible on a fast motorbike such as a PCJ-600 or NRG-500, and sometimes also require the character to lean forward on the bike for increased speed. In other jumps, too much speed may lead you to overshoot the landing area. There are also Insane Stunt Jumps, which aren't required for 100% and the amount of reward money depends on the difficulty of the stunt.
Evolution
Stunt jumps first appeared in Grand Theft Auto III, and have been in each game since. Early GTA games gave no indication to distinguish failed unique stunt jumps from those successfully completed. To address this, modders have developed add-on tools such as Demarest's Uniquecall to list or show on the map which jumps remain. Grand Theft Auto: Liberty City Stories shows each jump you've attempted on its map when you choose "Show Discovered Extras".
GTA III
This introduced stunt jumps. There are 20 stunt jumps spread throughout Liberty City, 4 on Staunton Island, 8 in Shoreside Vale, and 8 in Portland Island. Compared to later games, the stunt jumps in GTA III are easy.
GTA Vice City
There are 36 unique jumps in Grand Theft Auto: Vice City, and are most easily completed using the PCJ Motorcycle. In fact, some jumps cannot be performed using anything else. The jumps in Vice City are more difficult than those in GTA III, some being much longer and even extending over water.
GTA San Andreas
There are 70 unique stunt jumps in Grand Theft Auto: San Andreas, most are quite difficult. The majority are situated beside each other, with very few being isolated. These jumps are relatively easy to find throughout San Andreas, with fairly obvious take-off and landing areas. Completing the 70 Jumps is not necessary for getting 100%. This is the only game in the GTA Series that doesn't requires it.
GTA Liberty City Stories
There are 26 stunt jumps in GTA Liberty City Stories. They are spread evenly throughout the 3 islands.
GTA Vice City Stories
The PlayStation 2 and PlayStation Portable versions of Grand Theft Auto: Vice City Stories differ in the number of jumps. The PSP version contains 30 Stunts, and the PlayStation 2 version contains 36.
GTA IV
In the GTA IV version of Liberty City, there are 50 stunt jumps. Completing all 50 on the PS3 will bring the player two ticks closer to 100%, while on the Xbox 360, completing all 50 unlocks the achievement Daredevil, awarding 30 gamerscore. There are major changes in unique stunt jumps from the GTA III Era to GTA IV, the largest being that the player no longer collects money for doing stunt jumps. Another significant change is that instead of landing without crashing like in previous games, the player must land directly on the destination area.
Insane Stunt Jumps
A stunt is an unusual and difficult physical feat, or any act requiring a special skill, performed for artistic purposes. In the Grand Theft Auto series, since GTA III (2001), stunting is a popular pastime among the community, with feats usually involving various vehicles such as bikes, motorcycles and cars. Players who perform such acts are usually rewarded with an Insane Stunt Bonus, which is equal to a random amount of cash, depending on how insane the stunt is.
There are three 'ranks' of Insane Stunt bonuses, the higher ranks increasingly difficult to achieve. Firstly, the Insane Stunt bonus, which is the easiest. Next the Double Insane Stunt bonus, which is a little harder. Finally, there is the Triple Insane Stunt bonus, which is fairly rare without special conditions or cheats.
In Grand Theft Auto: Vice City Stories there is another called "Flameing Insane Stunt" which is awarded by doing an insane stunt that causes the vehicle to catch fire at some point prior to landing, ussually on take-off.
See also