The Energon Pub

Beast Wars: Basic Terrorsaur or his repaints Lazorbeak and Hydra.

Armada: Starscream, Megatron, Demolisher, Hoist, Blurr

Energon: Rodimus/Checkpoint, Strongarm, Starscream, Ultra Magnus, Ravage, Cruellock, Sledge, Kickback, Scorponok

Cybertron: Swerve, Ransack

Robotmasters is a nice little subline.

As for the best reps of the fiction:

Armada: PS2 game

Energon: Dreamwave

Cybertron: erm....

Beast Wars: Do I really need to suggest the show? I did like the comics and sourcebook too. Also the Universe/Wreckers books.

For the Unicron Trilogy in general: Cybertron Optimus Prime, Galvatron, and Primus.
The Movie lines thus far: Buster Optimus Prime, Leader Starscream, HA Jazz

Although for what Fansproject did with them later, Superion and Bruticus from both lines are close seconds.

CHUG: Voyager Optimus mold