@darekpawlo There is already a manga / novel with a familiar rabbit and also with a goblin.
But the latter manga translated chapters come out terribly slowly.
@darekpawlo: Probably because slimes has much cuter appearance/popularity in fantasy setting thanks to Dragon Quest (even Rimuru quoted 'I'm not a bad slime' from Dragon Quest)
Also slime has really extreme varieties among them (healing slime, acid slime, metal(Sans) slime, etc) which leave a lot of room for directions they can grow to.
Step one: get a slime.
Step two: level it up.
Step three: slowly melt the villagers one by one, while others are forced to watch it, waiting for their turn.
Eventually we should have a slime ranking. Rimuru (God slime), Sui (pew-pew slime), Slime Life (employee of the month), Kamitachi (clean that septic pit), Tensei Kenja no Isekai (pirate and mustache slimes), and Dragon Quest slime (top-tier mascot).