The following examples of failed experiments that produced valuable information
1) Bubble Wrap: The scientists were trying for trendy new textured wallpaper, they failed miserably ,however the new wrap was a breakthrough in packing industry
2) Pacemaker: During development of a heart rhythm recording device, Greatbach pulled out the miss sized small resistor which sounded like a human heartbeat and thus leads to development of pacemaker
3) Synthetic Dyes are also discovered during synthesis of antimalarial drug
4) Radioactivity : it was also a serendepity
5) Discovery of penicillin.