Need for Speed: World Discussion
Test Drive Unlimited, for example, has one.
It largely depends on how the game actually work. You can't expect people to make trainers that hack server-sided data such as money and exp.
It is, however, arguably possible to do a physical trainer like the good old Instant 1000mph, Instant Brake or even Never Busted. I'm not a trainer maker, though.
* Up to 400 new and updated trainers monthly
* Manage and update trainers through one app
* Request which games get new trainers
* Priority support with any problem