Ok, I found myself with some time on my hands, and noticed that there seem to be a lack of Canon character being picked up. Not that fan characters are in any way bad, but the Canons already have established relationships and pecking order that helps them to slot in smoothly. They also have more ability to take part in certain storylines, particularly the ones involving new technology and the like.
Now it may seem like this list is repeating information that is available elsewhere, but I thought it would be nice to collate it all in one place to make it more obvious. This is no way is supposed to suggest people not check up the roster lists and rules sections themselves, it's only a guidepost to show what's there to be tried.
Also I should point out I have a horrendous bias towards quirky or unusual characters over ones that are just hero types with guns or angry loners.
I recommend
http://www.tfu.info for getting stats for these, and the snarky yet informative transformers.wikia.com to learn more about them and what storylines they've been in in the past.
Fuzzimus Prime's list of Interesting Available Canon TFs
Aerialbots: Air Raid is a good choice for those who want to play a daring warrior who can fly, and Fireflight for those who want a foolhardy type that can get himself and others in a jam through sheer enthusiasm. Both have instant storyline potential as they're going to Earth shortly, and there's the future development of Superion to consider.
Technobots: Afterburner is your stereotypical Angry Autobot, Lightspeed is a starry-eyed guy for those who want to talk about 'after the War', and Nosecone is the completative type who thinks but is surrounded by a lot of unthinking action types. All have a potential future storyline in Computron. Right now they're one of the few big teams in Iacon, so they have some intrinsic military value.
Fembots: Arcee, Chromia, Firestar and Moonracer are available. I'd hardly say being a female transformer is particularly unique at this stage, but they do have immediate hooks in their 'Boyfriends' (Firestar x Inferno, Moonracer x Powerglide, Chromia x Ironhide, Arcee x Springer/Hot Rod/Chromedome/Anyone else who can talk tough).
Autobot Headmasters: While they don't yet have their Head gimmick, and there's no sign that they will anytime soon, there's still a large number of classic character you may remember from the Comics, like Brainstorm the ideas mech, Highbrow the condescending genius, Siren the Music-lover and of course, Nigthbeat the Private Eye (Trenchcoat not included). Don't expect your Nebulan partner anytime soon though.
Monsterbots: Repugnus is getting lonely....Grostusque is you happy-go-lucky type of guy, which Doublecross has split personality and can have long arguments with himself. Both should be pretty powerful (they are monsters).
Powermasters: Again, no partner, but there's an interesting set of character, with Getaway the escape artist, Slapdash the ditz, and Joyride the...Wildrider wannabe, from what I can see.
Autobot Pretenders: Again, you won't have your gimmick yet, but that storyline is proceeding and developments could be reasonably swift. Plus you've got such a wide range of personalities, from hypochondriac Chainclaw, big-talking Crossblades, two-brained Doubleheader, the guilty and insecure Gunrunner, the brash Landmine, the mad science type Pincher, the living-in-a-fantasy Sky High, and the thrill-seeking Vroom. How can there not be one of them you'd love to play.
Autobot Targetmasters: If you think you can make do with conventional arms (and everyone else does), the fussy arms specialist Crosshairs, the tired-of-war Pointblank, and the angry scientist Quickmix (with bonus ability to make stuff) would be interesting to see.
Other Autobots:
Everyone's favorite hipsterbot, Blaster.
The wierd-accented, space scout Cosmos.
The grumbling but ultimately jovial Gears.
The artistic engineer Grapple.
The friendly maintenance bot (and movie star) Hoist.
The adventurous master of holograms, Hound.
The endlessly complaining engineer Huffer.
The high-flying Powerglide.
The triple-changing, fearless scout Sandstorm.
The master of Land and Sea, if a little garbled, Seaspray.
The vain, slightly 'ho yay', Double-and-a-half-changer Tracks.
The WHAM noisy KAH-BOOOM never-say-quit YAZOWWWW Warpath.
The Combaticons: One of the best-equipped and trusted of the gestalt teams, it's just been revealed on the Polyhex thread that their Gestalt form is in the works. The lonely space-scout Blast-off, the sadistic interrogator Vortex, and the angry, violent, noisy Brawl (of mis-named in the movie fame), are all available.
Constructicons: One thing about playing a constructicon is that you'll never be just sitting around: Whether its building stuff or knocking it down, these guys are vital to the Decepticon war effort and are always in the middle of important matters. The demolionist Bonecrusher, the witch-with-his-own-cauldron Mixmaster, or the perennial underdog and scrounger Scavenger, are all available, and I can personally attest that they're fun to play.
The Monstercons: Without their pretender shells or their combining, they lose some uniqueness, but they're still playable.
Predacons: All of the Predacons bar Rampage are completely free, from the Stubborn-like-diamond Headstrong to the Happy Death-Pigeon Divebomb.
Seacons: The seas of Cybertron have been neglected it would seem: Perhaps taking one of these lovable fellows can change that?
Stunticons: If one wishes to take the over-achieving Drag Strip, then this team of psychos will be complete. Again, possibilities for future gestaltism.
Terrorcons: The contemptous Rippersnapper, the greasy Blot, the awesomely-names predator Sinnertwin, and the ultraviolent Cutthroat are all ready to monsterise the Decepticon offensive.
Decepticon Headmasters: Again, no Nebulans, but the orders-detesting Fangry, the proud-of-his-dirt Horribull, the 'Sabatouer' Squeezeplay, and the Triple-changing Horrorcons, the egotistical Apeface and the lazy Snapdragon, are ready to wreak havoc, most likely in the Tagan Hieghts with their pals.
Insecticons: The keep-shooting-till-there-only-smoking-legs Barrage and the manipulative Kickback are the 2 remaining of the recently-returned, specially-powered, kinda in trouble squad of vampiric assassins.
Decepticon Pretenders: With the Pretender process having been proven by the battle of Tagan, it's very likely that any of these characters, if active will go through the process of getting their shells fairly quickly. Thus the were-vampire thing Bomb-burst, the sometimes psychotic, sometimes noble Carnivac, the pirate-with-a-skin-condition Finback, the sadistic coward Roadgrabber, the psycho Skullgrin, the greedy Snarler, the ultimate heel Stranglehold, and the loner Submarauder could all end up some of the most impressive warriors in the Decepticon army!
The Premades: A Large number of interesting Seeker and Sweep ideas have been premade to help give more character options to players and fill obvious holes in the Decepticon ranks. If you were thinking of playing a flying decepticon, of any sort, it might be worth your while to check out
viewtopic.php?f=179&t=13092, to see if something there fits you.
Decepticon Targetmasters: A wide variety of evil people who shoot things lie in this grouping, from the A-Team villain Misfire, the 'trendy' Needlenose, the raging berserker Quake, the 'duelist' Sluslinger, and the mysterious Spinister.
Other Decepticons:
The Triple-changing Transport Astrotrain.
The dumber-than-rust pyromaniac Cindersaur.
The double-trouble Flywheels.
The mysterious, ambitious Gutcruncher (Rank 10 and he comes with an awesome spaceship!!!! Er....maybe in another RPG.)
The Triple-changer rogue, Octane.
The Energon Baron and Conservationist, Ratbat.
