I went with Aflatoxin, Dirk, and Graviton Mercenary. I have never ever used those cards in any deck in any format, whether pvp or pve, unless it was an oracle card. I think most of the rest of those I've at least considered using, if not actually used.
Aflatoxin: Several turns to kill a creature, and then you spam them with attackers to use against you? Ugh. Using it on your own creatures to generate cells is probably less efficient than boneyard/graveyard in most cases. Plus, aflatoxin is ridiculously overcosted.
Dirk: If the elements that gave +1 damage were different, this might be usable. But for one dark quanta you can get vampire stiletto, which kicks major butt, and for 2 death quanta you get arsenic. Any deck I would even consider using this in, I'd use short/longsword in instead.
Graviton Mercenary: For 1 more quanta, you can just use the sapphire charger, which is way better with momentum and +1 attack. Even the upped version is mostly useless; the one place it might work, speedbows, would be better off using black hole or pulverizer or something else instead.