The appearance of 'unusual' and 'common' next to each other in the title is a very rare occurance in itself.

Abscess Root

Adder's Tongue

Bedstraw

Bittersweet

Compass Plant

Devil's Bit

Dyer's Madder

Eyebright

Feverfew

Forget-Me-Not

Goat's Beard

Horehound

Horsetails

Jacob's Ladder

Jewelwood

John's Bread

Love Lies Bleeding

Mouse Ear

Paradise Gains

Queen's Delight

Shepherd's Purse

Snapdragon