Breacher: Your skills are focused entirely on negating, bypassing and circumventing walls. Sure these skills are invaluable for neutralizing threats with your high-caliber fire arms while remaining in cover, but the fact that they are engineered solely for use against walls results in you being overspecialized. Unless, of course, you can argue that the various objects around you are, in fact, walls. After all, a hostage is just a person being used as a
wall to deter you. Shields are just portable walls and armor is just a wearable shield, therefore armor is just a portable, wearable shield. And what about the fourth wall? It's even called a wall, thus you don't even need to contest your argument in order to start disrupting damage, healing and RNG functions with bullets.
Nekomancer: Using the power of dark magic, corruption and the almighty force of indefinitely spamming images of cats, you can distort the nature of the world. Corrupt you enemies to screw up their AI, dodge bullets by inducing lag via DoS. Dark magic encompasses forbidden spells as well as a limited-access developer interface. Just be vary that your powers tend to be difficult to fully control: modding and the dark arts tend to have high degrees of unpredictability and seeing as you are using both, sometimes in tandem, this uncertainty may screw you over when you least expect it.
Attorney: By adding unnecessary clauses, terms, conditions, general circumlocution and legal padding you can manipulate the rules to you advantage. And if you add so many that the GM starts getting a headache from trying to decipher what the fuck is supposed to happen, they'll be quite happy to smite your enemies with localized calamities if you get rid of the mass of bureaucracy you have dumped into the game. If circumstances won't allow you to start complicating the game, you can always just use your specialized sabotage equipment to neutralize your foes.
Gambler: You're not sure what you are or how you are even alive. Neither does the game. You are some sort of eldritch conglomeration of traits that are generally possessed by knights, liches, magical girls and subatomic particles. It isn't more difficult to kill you than anyone else. The issue is with keeping you dead. You exist in some sort of superposition between which means that
things that require life functions have a 50% of failure for you, dying forces you into a state of death but unless sufficient force is used, this will only be temporary. You can summon weapons into combat if required and delay RNG functions so that their outcomes are withheld temporarily.
Elf: You are a tree-hugging, pointy-eared, androgynous, bow-and-arrow using elf. It is quite easy for people to disguise themselves as an elves. Thus your "race" is quite upset by the amount of assassins, black operations units and spies who disguise themselves as members of your kind. At least, that's the official statement. Funnily enough, elves do not exist. The so-called "civilization" that you belong to exclusively consists of assassins black operations units and spies. People might suspect that some of you are actually human, but no-one will suspect that you are all human. You can used advanced weaponry and cast away your false limitation as long as the only people who survive are allies, if you drop your act, combat cannot end until all witnesses who are not allies are kept safely away in the respawn queue. You can also switch out your disguise and identity to reset all known knowledge of yourself.