Insignia

One of the universals across all Transformers continuities has been the use of insignia to differentiate members of respective armies, and sometimes sub-factions within armies or even individuals.

Generation 1

Prehistory

• 
  Ancient Transformer
  This is an ancient symbol that Shockwave found in the G1 Dreamwave comic. Although Transformers have been split into two races, they are one species, he claims.
• 
  Autobot
  This symbol appeared on the forehead of one of the Autobot leaders who spoke to Rodimus Prime within the Matrix.
• 
  Fallen
  This symbol was only used on the Titanium toyline representation of the Fallen. It was not used in The War Within or any other fiction.

Pre-War

• 
  Clench
  This symbol was worm by Clench and his team in Kaon's illegal pitfights prior to the Great War. After Megatron replaced Clench as team captain he retained the symbol for a time before developing the Decepticon insignia as his team emblem.
• 
  Security Services
  This symbol is used by the Autobot Security Services crew operating under Sentinel Prime and was seen on the flags draped over the coffins at the state funeral of operatives Fastback and Bumper.
• 
  Senate-related symbol
  This symbol was worm the crew of Senator Decimus' ship, as well as by Ratbat during his senatorial days.

The War Within

• 
  Autobot
• 
  Decepticon
• 
  Emirate Xeon
  This symbol appeared on the helmet of the departed politician Emirate Xeon.
• 
  Ultracon
  Used by Ratbat's group in The War Within era

The Great War

• 
  Autobot
  It seems likely that in the real world, the Autobot symbol was derived from a stylized drawing of Prowl's toy's head. In the Marvel Comics continuity, it was known as the "Autobrand" and was seemingly based on the face of the Last Autobot. In the original animated series, it was a mark of the Quintesson slave brand.
• 
  The Autobot symbol as it appeared on Generation 1 toy packaging.
• Decepticon It seems likely that in the real world, the Decepticon symbol was derived from a stylized drawing of Soundwave's toy's head. It has no given origin in either comic or cartoon, but in the latter, it presumably has the same origin as the Autobot symbol.
  Decepticon
  It seems likely that in the real world, the Decepticon symbol was derived from a stylized drawing of Soundwave's toy's head. It has no given origin in either comic or cartoon, but in the latter, it presumably has the same origin as the Autobot symbol.
• 
  The Decepticon symbol as it appeared on Generation 1 toy packaging. Note the bevelled detail in the center of the crest at the top - the model sheet of the symbol created for the G1 cartoon based on this version misinterpreted it as a third spike, and it appeared in the show rendered in this manner almost universally.
• Cybertron Guard This symbol represents the Decepticons under Shockwave's command charged with Cybertron's security. It was retroactively named in 2007 by TakaraTomy's World of the Transformers website, but unnamed in its original context. Divide and Conquer
  Cybertron Guard
  This symbol represents the Decepticons under Shockwave's command charged with Cybertron's security. It was retroactively named in 2007 by TakaraTomy's World of the Transformers website, but unnamed in its original context.
  Divide and Conquer
• 
  Wreckers
  This symbol was used by the Wreckers in the 3H Wreckers/Universe comics, and debuted in 2001. It is uncertain if prior incarnations of the team used this insignia or if it came into use after the signing of the Pax Cybertronia. Departure

Non-Cybertronian Insignia

• 
  EDC (cartoon)
• 
  EDC (Dreamwave)
• 
  Machination
• 
  Quintesson
  This symbol was featured as part of the decal set for the e-Hobby exclusive Overcharge drones.
• 
  Z Foundation
• 
  Zarak Consortium

Kiss Players

These symbols were used by the Sparkbots in Kiss Play Position.

• 
  Angela
• 
  Stardust
• 
  Zangetsu

Brazilian G1

These faction symbols were used in the Brazilian Estrela releases of the Microchange "Mini Car Robo" subline molds.

• 
  Optimus
• 
  Malignus

G.I. Joe Crossovers

• Cobra
  Cobra
• G.I. Joe
  G.I. Joe

Generation 2

• Autobot The G2 Autobot symbol seems clearly based on Optimus Prime. In the Marvel Comics continuity this change may have occured since the Last Autobot had come and gone.
  Autobot
  The G2 Autobot symbol seems clearly based on Optimus Prime. In the Marvel Comics continuity this change may have occured since the Last Autobot had come and gone.
• 
  Decepticon
  The G2 Decepticon symbol seems to be a stylized, updated G1 Decepticon symbol. Bludgeon's Decepticons adopted this symbol around 1991, apparently unaware it was also being used by the Cybertronian Empire that they would soon encounter.
• 
  Cybertronian
  This symbol was used by Jhiaxus's Cybertronian Empire, who considered themselves neither Autobot nor Decepticon.
• Cybertron Alliance This was only used in Japanese continuity to bridge Return of Convoy and Generation 2.
  Cybertron Alliance
  This was only used in Japanese continuity to bridge Return of Convoy and Generation 2.

Beast Era

Beast Wars

• 
  Maximal
• 
  Predacon
• 
  Predacon (Timelines)
  Worn by Razorclaw in Dawn of Future's Past.
• 
  Mutant
• Maximal Peacekeeper Worn by knight-like Maximal soldiers/peacekeepers in Beast Wars: The Ascending.
  Maximal Peacekeeper
  Worn by knight-like Maximal soldiers/peacekeepers in Beast Wars: The Ascending.

• Predacon (G1)

These symbols appeared on the walls of a transwarp shunt room used by Magmatron in IDW's Beast Wars: The Gathering. Although never explicitly stated, they apparently denote the original Predacon combiner team.

• 
  Razorclaw
• 
  Tantrum
• 
  Divebomb
• 
  Headstrong
• 
  Rampage

Beast Wars II

• 
  Moon
• Seacon Space Pirate
  Seacon Space Pirate

Beast Wars Neo

• Blendtron
  Blendtron

Beast Machines

• 
  Maximal
• 
  Vehicon
• 
  Dinobot
  This insignia replaced the spark crystals of the Beast Wars Neo toys that were introduced to the Beast Machines toyline.

Car Robots

• 
  Combatron
  Takara used this symbol to represent the Combatron (Decepticon in Robots in Disguise) sub-group in Car Robots—it's an upside-down Generation 2 Autobot symbol, which had been molded into the Black Convoy toy, a redeco of Generation 2 Laser Optimus Prime. The Hasbro version removed them and used the traditional Decepticon symbol. Though it can be briefly seen in the cartoon, this symbol does not "exist" in the English version.

Unicron Trilogy

Armada

• 
  Mini-Con
  This symbol hints at the origins of the Mini-Cons, in that the "M" is echoed in Unicron's face, with the border representing the planet-eater's orbital ring.
• 
  Unicron
  Used in Dreamwave's Armada profile book to denote Unicron-allied Transformers.

Energon

• 
  Powerlinx - Black
  Used by Optimus Prime and his combiner partners.
• 
  Powerlinx - Gold
  Worn by Mega-sized Transformers who can combine with fellow Mega- and Deluxe-sized Transformers.
• 
  Powerlinx - Silver
  Worn by Deluxe-sized Transformers who can combine with fellow Deluxe- and Mega-sized Transformers.
• 
  Powerlinx - Red
  Worn by Ultra-sized Transformers, who can combine with additional vehicle mode parts to form a "brute mode"
• 
  Powerlinx - Blue
  Used by the Air Team, the Construction Team, and the Destruction Team.
• 
  Team Ironhide
  An insignia worn by Ironhide and a group of Omni-Cons under his command in an episode of the Energon cartoon.
• 
  Unicron
  Seen in the background of Unicron's transformation sequence in the Energon cartoon.

Cybertron

• 
  Earth
  Seen on Cyber Keys that belong to Transformers from Earth.
• 
  Velocitron
  Seen on Cyber Keys that belong to Transformers from the planet Velocitron.
• 
  Jungle Planet
  Seen on Cyber Keys that belong to Transformers from the Jungle Planet.
• 
  Gigantion
  Seen on Cyber Keys that belong to Transformers from the planet Gigantion.
• 
  Cybertron Defense Team
  Used by Hot Shot, Red Alert, and Scattorshot, after their collective reconstruction.

2007 movie

For the 2007 movie, the Autobot and Decepticon factions were rendered in the steely gray seen below. Additionally- the Autobot and Decepticons were strongly associated with the colors blue and red, which led to the Autobot symbol appearing in blue in multiple media. Nonetheless the 'official colors' of said symbols remains red and purple.

• 
  Autobot
• 
  Decepticon
• 
  Sector Seven
  A Secret organization on earth that is trying to save humanity from the Autobots and Decepticons.
• Mountain Dew Robot An elite group of infiltrators determined to steal the All Spark for their own purposes.
  Mountain Dew Robot
  An elite group of infiltrators determined to steal the All Spark for their own purposes.

Transtech

• 
  Autobot
• 
  Decepticon

Shattered Glass

The alternate reality of the Shattered Glass timeline posits an army of evil Cybertronians united under the leering visage of a purple insignia badge... though probably not the one you were expecting.

• 
  Autobot
• 
  Decepticon

Transformers Animated

• 
  Cybertron Elite Guard
  This insignia is used by the elite forces under the command of Ultra Magnus.
• 
  Sumdac Systems
  The corporate logo of Isaac Sumdac's company, as seen in the foyer of Sumdac Tower.

Others

• 
  Autotot
• 
  Go-bot
• 
  Go-bot
• 
  My 1st Transformers

Unused concepts

• 
  Cobra/Decepticon
  Used for promotion of the comic, not in the actual story.

From Teletraan I: The Transformers Wiki, a Wikia wiki.