The Hobo Nickel
The Hobo Nickel is a sculptural art form involving the creative modification of small-denomination coins, essentially resulting in miniature bas reliefs. The US Nickel coin was favored because of its size, thickness, and relative softness.
Due to its low cost and portability, this medium was particularly popular among hobos, hence the name.
The most reputable Hobo Nickel was the Buffalo Nickel. Don't mistaken the term "Hobo Nickel" for only being Buffalo Nickels. It is any coin that is altered and sculpted.