Kiss

More of a "tongue-transferral process."

A kiss is a peculiar sort of human bonding ritual involving (sometimes mutual) oral contact. The reasons for this strange phenomenon are usually beyond the typical Transformer's understanding, resulting in many an uncomfortable line of questioning. Are these fleshlings transmitting data? Is it an energy-transferral process? Why are they doing it in my back seat?

The plot thickens. When properly administered by the correct agent, a kiss can provide an incredibly potent power boost to Transformers, with occasionally unpredictable results.

Marvel Comics continuity

Looks like he's about to round third base as well.

It has been stated on a few occasions that the kiss is an act of atonement for past perceived misdeeds. However, this information comes from a very small dataset, specifically the individual human named Jessie. While in the company of Buster Witwicky, she has repeatedly described the act of kissing as "apologizing". Since the use of this term has not been observed in use by any other human (other than Buster himself, seemingly part of an attempt to encourage continued kissing from Jessie), the conclusions one can draw are strictly limited. Brainstorm! Buster Witwicky and the Car Wash of Doom

Kissing is not limited to the humans of Earth. The ritual is also practiced on Nebulos by the Nebulans Gort and Marita. The Autobot Highbrow was able to witness this event, which caused a short but violent war between their race and the Transformers. Clearly volatile emotions surround this act. Highbrow, at the time, was not able to ascertain whether kissing was akin to a binomial data transfer, and even after binary bonding with Gort, answers have not been forthcoming. Ring of Hate!

Generation 1 cartoon continuity

ME GRIMLOCK SAY NO MEANS NO.

During the Golden Age, the Autobots were known to have engaged in kissing, as Orion Pax was kissed by his girlfriend Ariel. War Dawn

Astoria kisses Powerglide's face before parting. The Girl Who Loved Powerglide

The Junkions have adopted the human ritual of kissing, apparently after watching much of their television transmissions. Re-Cycle even kissed the Dinobot leader Grimlock. This act greatly confused the Dinobot leader, and caused him to reassert his status as "king". The Transformers: The Movie

Blaster described the (to him) pleasing sound of the harmony as "a musical kiss". Carnage in C-Minor

Hellbat used hugs and kisses to distract Guyhawk from just hearing him plot to get rid of him. Rescue! Guyhawk

Beast Era

The Maximal Silverbolt and the Predacon Blackarachnia have been nearly observed kissing at several opportunities, but none of our recording equipment has been able to successfully capture it at the exact moment of contact. Again, as on Nebulos (see above), the act created an amount of irritation amongst the participants' peers. The Agenda (Part 1) The after-effect of the kiss has been observed, however. When applied to the Maximal following Blackarachnia's Transmetal 2 upgrade, it seemed to disorient him for a moment and shoot small amounts of energy through his cranial module. Crossing the Rubicon

Let's not even get into Rattrap and Botanica. Spark of Darkness

And we aren't even going to touch Rattrap kissing Rhinox after he fell into his arms. The Agenda (Part III).

Kiss Players

Oh God. You don't want to know. You shouldn't know. But your curiosity will get to you. Note: We apologize for any damage caused to your psyche or immortal soul.

Transformers (2007) movie

Sam Witwicky and Mikaela Banes could be found macking on Bumblebee's hood (note: he was in car mode) to the strains of Linkin Park, as the other Autobots watched. Transformers (2007)

Transformers Animated

Blackarachnia and Optimus sometimes look to come close to doing this but it tends to just be a trick on Blackarachnia's part. Along Came a Spider Black Friday

Grimlock has shown interest in wanting to steal a kiss from Blackarachnia. Black Friday