Recently I made several vessels from plastic containers. Here is a little vase:
The vessels were made following Make an Art Bowl from PET Bottle from Instructable user Gulguvenc; all the tools you need are scissors, a candle, and a soldering iron/wood burner. I'm using one small bowl made from a flat piece of plastic to hold my finger picks.
I am rescuing plastic containers from my recycle bin and also the trash at work and have a few more that need upcycled. They are pretty fun to make, watching the plastic melt is soothing.