My tuning process is as follows - I have around 100 cars and have tuned them all without testing (;)). I am progressing through the 168 single player championships and if I find a car that wins in career with little effort and feels good then I share it. If not I fine tune and hope the next time that championship comes up the car feels better.
So any tune I have shared I find an easy win in career.
I am writing this post from memory and will edit with corrections later so some classes may be wrong.
Most tunes are all rounders ie suitable for any race types. Most are AWD but tuned to turn.
Subaru WRX 05 (set a top ten time in the Clubbed Up rivals event)
Subaru Legacy RS (was temporarily in the top ten in Clubbed Up until my final WRX run)
Volkswagen Corrado VR6
Chevy Monte Carlo SS
Renault Clio Williams (2 x FWD tunes for tarmac)
Lancia Fulvia (FWD tune for tarmac)
BMW M235i (RWD tarmac tune)
Ford Escort RS1800
Subaru 22b (tuned for the tarmac events at Nice)
Lancer Evo VI
Bmw 2002 Turbo (tune request - understeers a little but the requester likes it that way)
Mercedes A45 AMG Day One livery
Mercedes E63 AMG
C2 Corvette (RWD for tarmac)
Subaru WRX 05 (2 versions for tarmac tracks, tuned for Clubbed Up 3)
Subaru 22b (tuned for Clubbed Up 3)
Maserati MC12 (tuned for Clubbed Up 3)
2013 Audi S4
2006 Audi RS4
Ford Capri ( lively and fun but can be driven tamely as well)
Ferrari 2003 Challenge Stradale (has proven to be an absolute beast online)
I will add to this list any that I think are worthy.
UPDATED FOR THE FOLLOWING RALLY TUNES:
Subaru BRAT (3 x rally tunes) - all tuned for Temple Brawl
Ford Lotus Cortina (v1 uploaded, there will be a v2 and this car will be useful on leaderboards)
Ford Bronco tuned for B class, Sisteron, East Plains Cross Country
Subaru BRAT (v1 tune but probably final) tuned for Temple Brawl
IDx NISMO tuned for West Trail Rampage
Nissan GTR 71
Jeep Wrangler (awesome lobby car)
Ford Escort RS Cosworth 92 tuned for the Cliffside Climb rivals event on Storm Island.
Mercedes 300SL RWD for Clubbed up 2 (a little less user friendly than the Camaro but quick if you get it right)
Chevy Camaro 70 RWD for Clubbed up 2 (plus a stock hood version)
Subaru 22b from Sugar Hill shared. Clutch users - you need to hold clutch in and dump on GO otherwise it bogs a little on launch. After that its a rocket ship
Ford Bronco tuned for Castelletto, Hillside Cross Country
IDx NISMO tuned for West Trail Rampage (also works well in monthly rivals this month at Hillside Cross Country. was in the lead until the Alfa’s showed up)
Shelby Raptor tuned for Temple Climb
Subaru 22B (currently holds a #2 at one of the cross country circuit races and definitely has the #1 in it)
Subaru WRX 08
Ford Escort 92 (Abbey Cross Country)
Ford Ranger (will probably get an update as its not quite there yet)
Ford Focus 09 (a little slippery still but has a good time on one of the Cross Country circuits)
Ford Focus 09 v2 (rally)
Ford Focus 09 v2 no aero (rally)
Ford Focus 09 v3