G1
Swindler traded his time-travelling stuff to get shot. (He loves pain, apparently!)
CliffJumper has suicidal tendencies.
Bumblebee kept being told to 'buzz off'.
Wheeljack gets his name from his rather nasty habit of leaving decepticons on the bricks.
Overload did way too much shopping in the sales.
Convoy kept thinking he was leading the pack. (Yeah, I couldn't think of one for Optimus Prime so I used his Japanese name instead)
Punch/Counterpunch is a paranoid schizophrenic.
Inferno is a pyromaniac who loves to go up in flames.
Grapple used to be a pro wrestler.
Devastator told Megatron he didn't love him anymore (LOL, just kidding)
Tailgate is always too impatient in the traffic jams.
Trypticon is hallucinating all the time (Don't do drugs, kids!)
Detour is always taking the wrong turnoff.
Armada
Tidal Wave tripped up on a coral reef.
BackTrack keeps forgetting things and has to retrace his steps.
Spiral did a doughnut for too long (Silly girl...At least, the transformers wiki says she's a girl)
Iceberg sunk the titanic all by himself.
Sparkplug blew a gasket.
Smokescreen used the wrong type of fuel.
Oval is named after the shape of one of his rear wheels after a lot of jumping around.
Waterlog lost all engine power and left his windows open. Need I say more?
Finally, the 2007 movie
Blackout: Accidentally stepped on a power station and pitched more than half of a town into darkness!
Swindle: Maybe he cheats people out of their money from buying his transforming toys?

(Just going with the majority on that one, I've never even come close to a movie Swindle)
Dropkick: I dunno, maybe he tried to imitate Sam from the movie and kicked another bot's severed head over the horizon?
Barricade likes boarding up windows on shops and locking doors. I guess he's preparing the area for what's to come.
Okay, that's me done. Sorry if it's a little big...Once I get going with this stuff I don't really stop until I run out of ideas.