This word has two plural forms, bandits and banditti.
Plural brothers, when referring to members of the same family; brethren, when applied to members of the same church or society.
Die
Plural dies, when the stamp with which seals are impressed is meant; dice, the cubes used in playing backgammon.
Herring
The plural is herrings, but shad, trout, bass, pike, pickerel, grayling, have no plural form. “I caught three bass and seven fine pickerel this morning.”
Grouse
The names of game birds, as grouse, quail, snipe, woodcock, usually take no plural form.
Pea