One of my favorite materials is beat up, trashed, colorful ball pit balls ( aka "dirty balls"). They're definitely throw away plastics, as they generally can't be recycled, and it's hard to find another use for them after their original purpose is no longer an option. But I use these old toys to make my hoop earring beads, and I use whatever is leftover from that to make the pigment for my trash stud earrings - like these! Don't worry, all plastics are cleaned and sanitized before use.
 
 
Approximate Measurements:  6.6 x 4.6 mm
Ear Wire Metal: hypoallergenic, nickel-free stainless steel post
Material: bright blue ball pit balls, plant based bio resin. 
Shape/Style: teardrop
Color(s): blue, silver