Once upon a time, during my misspent youth, I vaguely remember a guitar or bass player breaking his last pick (of many) in the middle of a song.  He reached into his pocket and pulled out a coin or something to  finish the song.  I think it was the last song of the set, but I can't remember exactly what the item was. 
 
I'm not a guitar player and I'm not sure what made me think of that event today, but it inspired me to start this thread.  I hope it will amuse you. 
 
The first thing that I thought of that wouldn't work well as a substitute pick: 
 
A cheese quesadilla. 

An Oreo cookie. 

Tortilla Chip....

A Dremmel saw blade.  It would probably ruin the guitar strings even if you managed to avoid marring the finish of the guitar. 

A slice of becan. 

When I ran out of picks, I've used (waaaay back in the day) those bread plastic ties thingamajiggies.....the little spikey edges always seemed to get caught on the string......
 
 

 

A pancake. 

a moose.

Beagle
a moose.

Yeah, those antlers can be a little thick and inflexible--then he keeps moving his head around. 

an El Camino.