Uh... Harmful?

Hedgehogs?

Harmful...dem quills tho.

Windows Blue Screen?

DEADLY.
...no but in all seriousness, can I say it'd be neither?

Needles?

Harmful.

Stepping on a lego?

Deadly

Hitting your elbow on something.

Harmful, I guess.

Mirrors? (If you think about their edges.)

Harmful or deadly? (you can break them)

Brick wall?

Harmful.

Stepping on glass?

Harmful.

Nuke?

Deadly.

Porcupines?

Harmful, I think.

Sea serpent?

Uh... Harmful?

Nuclear Bomb?

Deadly.

Knife?

Harmful.

Being stabbed with a pencil?

Harmful.

Shoving a pencil up your nose?

Harmful??? ??

Smashing your hand through the door?

Harmful.

Choking?

deadly

A pig with a blood nose :D

Harmfull

Carnivorious MO

Deadly...

Mouldy Radish?