Sniper trick.

Shoot the glow.

I agree with Soul.

Loosing the horn is very bad.

Really the only lost horn I have seen on MLP was Sombra losing his at the Crystal Empire battle. It did break off flying away as he flew the other.

I would guess his power remains in the horn so if some pony were to find it.......?

I did try this a few times in Viet Nam. I shot one time at a small light. I think it was a flashlight. I more guessed the aim barely seeing the cross hairs but I did try it!

There is a bit more ambient light here.....the sniper shot the glowing tip.

From unicorn magic to earth pony......in one shot.

Damn!