Definition of "Obscure": for the purposes of this discussion I am using the Obscure Transformers Website's definition of "obscure" as in a Transformer that only appears in one medium.
e.g. only exists as a toy but nothing else, only exists as a comic book character but nothing else etc.
An example of an Obscure Transformer is Spanner, the neutral Cybertronian architect of the Decepticon Spacebridge. This character has only ever existed in the G1 comics and no other media. He never appeared in any cartoon or any other comics (e.g. IDW) and has yet to receive a toy. Because he currently only exists in one medium it makes him Obscure. e-Hobby was one of the first to start making formerly Obscure Transformers not Obscure with toys like Hauler being made! Hauler! Since then we've had an increasing number of Transformers escape obscurity by appearing in new media (e.g. IDW comics) and/or receiving toys.
e.g. Ironfist, Dazzlestrike etc.
This means that the list of remaining Obscure Transformers continues to dwindle, so... who's left?
I thought it would be interesting for us to pool our collective knowledge and make a list of remaining Obscure Transformers - those who continue to solely exist in just one medium. I will update this list as more names are contributed in this discussion. But here are some that I can think of:
Cybertronians
* Aftershock
* Airburst
* Aurora
* Beta - she's mentioned in other media but does not appear in them
* Buildup
* Bulletproof
* Centurion
* Chameleon
* Claymore
* Comeback
* Corkscrew
* Corona
* Covert
* Decepticon High Council
* Deflector
* Discord
* Failsafe
* Firefight
* Flashbang
* Froid
* Fulcrum
* Fullspeed
* Fusion
* Geomotus
* Gristle
* Hailstorm
* Hawkeye (Armada)
* Highgear
* Highjump (Armada)
* Horror Show
* Horsepower
* Jumpstart
* Kickback (Armada)
* Knockdown
* Lock-On
* Longarm (Mini-Con)
* Longview
* Lookout
* Man of Iron
* Munitia
* Navigator
* Nullifier
* Overlord (Marvel)
* Overwatch
* Pressurepoint
* Rangefinder
* Red Star
* Rotorbolt (G1)
* Rubble
* Sandstorm (G2)
* Safeguard (Armada)
* Shepherd
* Shieldwall
* Shockpunch
* Skirmish
* Sky Creeper
* Slapshot
* Slipstream (Armada)
* Smackdown
* Spanner
* Sparkjump
* Springarm
* Stronghold
* Sunder (G1)
* Telus
* Trachis (a.k.a. the Student)
* Tractor
* Twister
* Valve
* Warrior
* Warmonger
* Warwolf
* Watchdog
* Wheelarch
* Wheezing Arrow
Non-Cybertronians
* Alcazar, John (Dr.)
* Altman (PDP Detective)
* Barnett, Charlene
* Barnett, Stephen "Stevie"
* Becker, Rachel
* "Berko"
* B'hgdad
* Big Top
* "Bomber Bill"
* Boyd, Jason
* Brown, Casanova
* "Burn-Out"
* Cahnay, Augustus "Auggie"
* Carlo, Verity Simone
* ???, Charlene (associate of Jake Lomax)
* ???, Charlene (the girl who loved Skids)
* ???, Clifford
* Colton, Jacob "Jake"
* Conroy, Matthew "Matt"
* Dalrymple, Jacob "Jake"
* Dialonzo, Hector - Dynamo
* Dietz, Clifford "Cliff"
* ???, Dwight
* "Ed" - worker at Sherman Dam [More Than Meets The Eye, Part 2]
* "Ed" - worker at solar power station [Transport to Oblivion]
* "Ed" - archaeology student [Legends anthology; "Paddles"]
* ???, Evan
* Fairchild, Edward "Eddie"
* ???, Felix
* Greco (PDP Detective)
* Harding, Morgan (Dr.)
* Haley, Ken (Dr.)
* Horton, Randall "Randy", a.k.a. "Roadhog"
* Jamal (HRH Prince), a.k.a. "Hassan"
* Lomax, Jacob "Jake"
* Ludwig, Stephen "Big Steve"
* Minkler, Martin "Marty"
* Morris, Edward
* Nergil (HRH King)
* "O"
* Poole, Charlene
* "Poplock"
* "Rocksteady"
* ???, Sierra
* "Skunge"
* Teranova, Jonathan "Jack" (Dr.)
* Welles, Charlene
* Williams, Jacob "Jake"
Generic Transformers
The difference between a Generic and Obscure Transformer is that Generics are never named. They're just background filler characters or generic "Gumbies" and at times, cannon fodder (e.g. Sweeps, Junkions etc.) It would probably be easier for us to list which formerly-Generic Transformers now exist in other media. Many of them may be named now but they were never named in their first appearance (they were originally generic). Compare Alpha Trion with Sunstorm - both initially only existed in the G1 cartoon but Sunstorm was never named. He was just a generic orange/yellow background Seeker, whereas Alpha Trion was named and even given a background story. Alpha Trion was Obscure but Sunstorm was Generic (both are now neither). So here are some formerly-Generic Transformers that I can think of...
* Acid Storm
* Bitstream
* Hotlink
* Sunstorm
Anyway, this is just the tip of the iceberg. I know that I've mostly focused on G1 (and even then I know I haven't covered them all) - and other continuities like Animated, Bayformers, IDW etc. have tonnes more. So let's add to these lists!