A mouse trap
4 eye hooks
2 bic pens (the smooth kind)
2 tops from pop cans (for the serious perhaps washers, or otherwise any other bendable metal)
some string (not pictured)
4 CDs/DVDs (expendable ones). Here 3 CDRs and a blank transparent thing from the top of a spindle. I hear DVDs are a bit lighter, but I'm not optimizing that hard.