Tough, but like the challenge of the repaints...

1. Flash
2. Hurricane
3. Boss (could be a Hound repaint)
4. Scorch
5. Rotorstorm
6. Thunderclash
7. Snare
8. Falcon
9. Skydive
10. Talon
11. Stalker
12. Skyquake
13. WFC Ratchet
14. WFC Ironhide (Ratchet repaint)
15. WFC Prowl
16. WFC Dead End (Prowl repaint)
17. Animated Earth mode Ironhide
18. Animated Kup (Earth Ironhide repaint)
19. Animated Trailbreaker (Earth Ironhide repaint)
20. Animated Yokietron (Samurai Prowl repaint)
21. Animated Tigatron (Animated Blurr repaint)
22. Animated Omega Supreme
23. Animated Lugnut Supreme (stolen from Sky Shadow, repaint of Omega Supreme)
24. Animated Zeta Supreme (repaint of Omega Supreme)
25. Animated Skybyte
26. Animated Sharkticon (Skybyte repaint)
27. RID SkyByte
28. RID X Brawn
29. RID Sideburn
30. RID Prowl
31. BW Tarantulas
32. BW Rhinox
33. Animated Chromia (Arcee repaint)
34. Animated Pipes
35. Animated Huffer (Pipes repaint) [Never get past Nintendo!]
36. Animated Mirage
37. Animated Drag Strip (Mirage repaint)
38. G1 Emirate Xxaron
39. G1 Nightbeat (IDW styled)
40. G1 Hardhead (IDW Styled)

So hard to narrow it down, and not even 100% happy with my selections. Would never happen either, too many same named characters. Maybe some IDW Wreckers would have been better...