Robert Williams with some of his collection of WWI Pickelhauben.
The Pickelhaube (plural Pickelhauben; from the old German Pickel = "point" or "pickaxe", and Haube = "bonnet", a general word for headgear) was a spiked helmet worn in the 19th and 20th centuries by German military.
As a kid, I was obsessed with these helmets. I always made sure I saw this one featured in the ending credits of Hogan's Heros. I would still like to have one.