This post contains everything you need to know about GTA V stunting. (Currently updating...)
Video Tutorials_________________________________________________________________________________________
GTA V - How to get more airtime with any motorbike [tutorial] GTA V -How to do a fast back flip with any motorbike[tutorial][How to wallride in GTA V]
How to go faster in any car, using Franklin's ability (Single Player)[How to grind in GTA V]
MOTORBIKES_________________________________________________________________________________________
Bati 801 / RR + Fastest motorbike
+ Good at pulling wheelies
The Bati is the bike of choice for most stunts, it has the highest top speed and thus the most potential for landing higher and further stunts. If it cannot wheelie high enough for a particular bump then try the Ruffian.
Ruffian+ Best at pulling wheelies
+ Second fastest motorbike (as far as stunting is concerned)
+ Slightly better acceleration than Bati
The ruffian is the most versatile bike; its speed, acceleration, and wheelie abilities make it great for any stunt, and it excels at high bumps which the Bati cannot reach.
Akuma+ Best acceleration
- Sucks at pulling wheelies
Good for short runup ramp or ramp to bump stunts.
Sanchez+ Arguably the best at wallriding
- O.K. at pulling wheelies, not great compared to Bati / Ruffian
CARS_________________________________________________________________________________________
Adder+ Fastest land vehicle
- Harder to handle around corners
The adder is the best car for stunting as it has the highest top speed and although the handling is not the best, franklin's ability easily remedies this.
Entity XF+ Second fastest land vehicle
+ Excellent handling
+ Better acceleration than Adder
The Entity is better for races but the Adder wins for stunting since handling does not mater as much, when using franklin's ability at least. It is certainly not bad, but has less potential than the Adder, although it may outclass the Adder in GTA Online.
Cheetah+ Very low to the ground, making it the easiest car to bump into
+ Great handling
The cheetah is best for bumping into with a motorbike or z-type as it is low to the ground, not bad for stunting by itself, but outclassed by the Adder and Entity.
Z-Type+ Can bump small bumps and stairs
+ Can bump other cars
The Z-Type is the only reliable car that can bump small bumps and also bump cheetah's very well.
BICYCLES_________________________________________________________________________________________
BMX+ Highest bunnyhops
+ Best at pulling stoppies
The BMX is the bike of choice as it can bunnyhop high and stoppie well, the two most important aspects of bicycle stunting. The high bunnyhop also means that it can jump straight into curved walls for wallrides, whereas the scorcher cannot.
Scorcher (Mountain Bike)+ Faster than BMX
+ Better at bumping from a wheelie
- Low bunnyhops
- Slightly worse at pulling stoppies than BMX
The scorcher may be faster than the BMX but has less potential due to its poor bunnyhop height and slightly worse stoppie capabilities, but some stunts may suit the scorcher better. It is also better / easier to wallride with due to its speed, although it cannot jump straight into a curved wall like the BMX, rather it has to ramp or bump into one.
UPDATE (30th April 2015): Please note that most of these tips & tricks are out of date, and do not represent what we know in 2015. The same goes for any of the replies below. Check the new topic for updates!
GTA V Basics Topic -
http://www.gtastunting.net/index.php?topic=67844