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