Several objects are useful in this game, but are not vital to complete the adventure. Just for the record, these are..

CLOVE OF GARLIC - Kills bats

INSECTICIDE - Kills Spiders

BIRD SEED - Kills...er...Birds

PICKAXE - Unblocks tunnel, to get dagger

HARD HAT - Destroys falling stalactites

EMERALD - Drop on yellow statue to enter tomb