3rd Party Checklist

Beezleboss
Devil Horns Custom Kit (Classics Cliffjumper accessories)
Growing Pains Custom Kit (Classics Bumblebee accessories)

BTS Toys
Mobile Command Base (Classics Optimus accessory)
Nemesis Motion Base (Classics Nemesis Prime accessory)
Teletran Kit (Classics figures weapons/accessories)
Matrix of Leadership (G1 Prime accessories)
Sonicron (Soundwave)
Savage and Nightfang (Ravage and Ratbat)
Tremor and Frequenzy (Rumble and Frenzy)
Yin and Yang (recolors of Rumble and Frenzy)

CHMS
Air Warrior (Classics Seeker recolor)
Chromia (Animated Arcee recolor)
Sunstorm (Orange version)
Paradron Medic (Animated Arcee recolor)
Rainmakers (Classics Seeker recolors)
Sunstorm (Yellow version)

FansProject
Classics Cliff Conversion Kit (Classic Cliffjumper add-on)
ABT Optimus Prime Upgrade Set (Alternators Optimus add-on)
City Commander (Trailer/Armor Classics Ultra Magnus)
Aerial Team Appendage Add-On Kit (Energon Superion Maximus add-on)
D.I.A Convoy (Trailer/Armor for Henkei Convoy)
G3 Trailer (Classics Optimus Trailer + Classics Weapons kit)
Powered Commander (Henkei Convoy Trailer/Armor)
Shadow Commander (Universe Nemesis Prime Trailer/Armor)
Defender (Springer)
Explorer (Blast Off; also needed for the Bruticus Maximus kit)
Munitioner (Swindle; also needed for the Bruticus Maximus kit)
Protector (Classics Rodimus Trailer/Armor)
Sidearm (Targetmaster Firebolt)
Backfiery (Kickback)
Blesser (Sidearm recolor)
Flameblast (Fireshot)
Shadow Scythe (Protector recolor)
Stormbomb (Bombshell)
Thundershred (Shrapnel)
Warcry (Growl)
Assaulter (Broadside)
Steel Core (original character)

Headrobots
Cobra (Headmaster)
Hothead (Duros)
Mixcoatl (Nightrider recolor)
Nightrider (recolor of Cobra)
Snake (Cobra Commander Headmaster)
Blood DX (ROTF Bludgeon Upgrade Kit)
Butcher (Classics Onslaught)
Stronghold (Fortress Headmaster)
Toxin (Nightrider recolor)
Centurian (Spike Headmaster)
Courageous (Brave Headmaster)
Garrison (Grand Headmaster)

Mastermind Creations
Annihilator (Black Commander recolor)
Commander (Hearts of Steel Optimus Prime)
Awakening (Prototype Hearts of Steel Starscream)
Cyclops (Hearts of Steel Shockwave)
Screecher (Hearts of Steel Starscream)

TF Club
Gear of War (Classics and Universe Weapons/Accessories Set)
Hot Flame vs Screamer (Hot Rod and Starscream)
Dr. Crank (Hook)
Exgraver (Scavenger)
Heavy Labor (Long Haul)
Mad Blender (Mixmaster)
Neckbreaker (Bonecrusher)
Structor (Scrapper)
Hercules (aka Devastator when you have all 6)
Optiaim vs Megashoton (Optimus Prime and Megatron)
Iron Army (Power Core Combiner Limbs)
Photron (Reflector)
Rage of the Hercules (Add-On Kit for G1 Devastator)
Ultra. vs Warp. (Targetmasters Ultra Magnus and Skywarp)

ToyWorld
Hegemon (Megatron)

X-Transbots
Glider/Air Robot (Powerglide)
Power Rat (Glider/Air Robot recolor as a Cobra Rattler)
Wild Child/Explorer (e-Hobby Bad Boy)
Destroyer (G1 Devastator Accessories)

iGear
Attack (MP Thrust)
Bee (Legends Bumblebee)
Black Rager (Rager recolor)
Delicate Warrior (Arcee)
Elegy (MP Dirge)
Evil Leader (MP Shattered Glass Optimus Prime)
Faith Leader (MP Optimus Prime)
Jet (MP Ramjet)
Presser (Impactor)
Lightning (MP Thundercracker)
Medical Specialist (Ratchet)
Nemesis Leader (Nemesis Prime)
Rager (Huffer)
Shadow Assassin (Nightbird)
Shafter (Erector)
Spray (Seaspray)
Hench (Brawn)
Storm (Sunstorm)
Traitor (MP Starscream)
Ultra Leader (Ultra Magnus)
Weapon Specialist (Ironhide)

Impossible Toys
Alicon (Allicon)
Alpha Trion (Alpha Trion)
Arbilus (Arblus)
Kranax (Kranix)
Kremzeak
Medic (Paradron Medic)
Nightbird (Nightbird)
Quint-01
Quint-02
Quint-03
Quint-04
Quint-05
Valkyrie (Arcee)

Junkion Blacksmith
Broad Caster (Blaster Headmaster)
Destruction Lord (Megatron Headmaster)
Earth Commander (Ultra Magnus Headmaster)
Evil Commander (Nemesis Prime Headmaster)
Infinity Warfare (Predaking Accessories Kit)
Justice Leader (Optimus Prime Headmaster)
Tactical Officer (Soundwave Headmaster)
Hyper Tactical Officer (Soundblaster repaint of Tactical Officer)

JustToys
Bombardier (?)
Commander (Grimlock)
Desert Warrior (Snarl)
Flamethrower (Slag)
Great Charger (Greatshot)
Jungle Warrior (Sludge)
Military Transport (Astrotrain)
Solo Assault Group (Sixshot)
Ultimate Fire (GreatShot)

MakeToys
Battle Tanker (RTS G2 Optimus Prime Upgrade Kit)
Bomber (Powerglide)
Bulldozer & Excavator (Bonecrusher & Scavenger)
Mobile Crane & Dump Truck (Hook & Long Haul)
Wheel Loader & Mixer (Scrapper & Mixmaster)
Giant Type-61 (Devastator when you have all 3 sets)
Hover & Bomber (Seaspray and Powerglide)

Perfect Effect
Buzzer (Buzzsaw)
Kingbat (Ratbat)
Laser (Laserbeak)
Ninja (Rosanna)
RC (Pink Arcee)
RC Battle (Blue Arcee)
Scouting Force X (Reflector)

Renderform
Blaster (Upgrade Kit for Universe Blaster)
Bumper (Uprade Kit for Classics Bee)
Darkwind (Upgrade Kit for Universe Darkwind)
Goldbug (Uprgade Kit for Generations Bee)
Hubcap (Upgrade Kit for Classics/Generations Bee)
Skyfall (Upgrade Kit for Universe Skyfall)

You completely missed of, the third party parts creator, known as Dr Wu, they made some nice little upgrades for TFs, mainly on the weapons side of things, thou they did a replacement face for TFP RID Wheeljack to give him a face without the plate over it, they have also made some swords based on concept art of one of the thirteen, they done guns for FE Op, as well as blades that aren't flimsy but solid!

There's a relatively unknown group called Dream maker that created two separate kits for WFC Op & Megatron, both called Warriors from Cyborgtron!

I searched several websites for a comprehensive list of 3rd party transformers available and found this half-ass suitable one that I copy/pasted here. I was well aware then that it wasn't all inclusive and not everybody was invited to the party, so to speak. But I'll update it eventually....but keeping up with the major items is the most important thing. That's why i haven't really included any head kits, weapons kits, exc....in the 3rd party forum so far. Mostly just trying to post up what I considered the best renditions/recommedations of those particular G1 characters made so far are. I need to get around to Arcee, the minibots and so much more. But I like the pace I'm getting the threads up right now as it gives others time to reply or research the figure themselves.