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 (ancient)
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's symbol
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.
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 (War Within)
Decepticon (War Within)
Emirate Xeon
This symbol appeared on the helmet of the departed politician Emirate Xeon.

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, the Autobot symbol was seemingly based on the face of the Last Autobot. In the original animated series, it was a mark of the Quintesson slave brand.
..........File:Symbol autobot reg.jpg

Decepticon

It seems likely that in the real world, the Decepticon symbol was derived from a stylized drawing of Soundwave's toy's head. The model sheet of the symbol created for the G1 cartoon misinterpreted the bevelled detailing of the top of the symbol as a third spike in the center of the crest, and it appeared in the show rendered in this manner almost universally.
........File:Symbol decept reg.jpg

Cybertron Guard

This symbol represents the Decepticons under Shockwave's command charged with Cybertron's security. Note: The term 'Cybertron Guard' was created in 2007 by TakaraTomy's World of the Transformers website, retroactively declaring the symbol in the 1984 episode Divide and Conquer to be the Cybertron Guard symbol. 'Cybertron' refers to the planet.
File:Shocksymb.jpg

Wreckers

Non-Cybertronian Insignia

EDC (cartoon)
EDC (Dreamwave)
Machination
Quintesson
Z Foundation
Zarak Consortium

KISS Players

Sparkbots

Brazilian G1

Optimus

Malignus

G.I. Joe Crossovers

Cobra

File:Cobralogo.gif

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.

File:Auto-g2.png

Cybertron Alliance

File:Cybertron-federation.png

Cybertronian

This symbol was used by Jhiaxus's Cybertronian Empire, who considered themselves neither Autobot nor Decepticon.

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.

Beast Era

Beast Wars

Maximal

Predacon

Predacon (G1)

From IDW's Beast Wars comic books

Predacon (Timelines)

Worn by Razorclaw in Dawn of Future's Past.

Mutant

Beast Wars II

Moon

Seacon Space Pirate

File:Space pirate seacon sign.jpg

Beast Wars Neo

Blentron

File:Blendtron symbol.png

Beast Machines

Maximal (Beast Machines)

Vehicon

Dinobot

Robots in Disguise

Japanese Decepticon

Takara used this symbol, to represent the Decepticon (Combatron) sub-group in Car Robots- it's an upside-down G2 Autobot symbol, which had been molded into the Scourge toy, a redeco of G2 Laser Optimus Prime. The American 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 American version.