Only bone should be used for nuts.

Only bone can give you the proper tonal characterics that you require for your style of playing.

Use whale bone for a fluid style.

Use tiger bone for a more aggressive sound.

Use chicken bone for plucking.

Use mammoth bone for a heavy bottom.

Use wolf bone for playing Duran Duran.

If someone ever finds a partly evolved animal this would be ideal for eclectic styles.

Etc?