I use pennies. Just plain ole' simple U.S. currency. Have for years.
Not to be different, but started using them when I ran out of picks one time at around the age of 15 or so.
The only real drawback, is that they can create unwanted overtones sometimes...especially when recording. So in order to avoid a ton of that, I've worked on a lot of hybrid picking techniques and using my middle, ring, and pinky fingers on my right hand....and using a LOT of legato-style phrasing.
As a result, if I do use a plectrum, it's gotta be as heavy as it gets....and I don't use the "pointy" end of it...rather the backside.