One thing that I love to find when going around flea markets and garage sales are old flat bicycle multi tools.
They are often overlooked by the seller because they don't know what they are and they can be had on the cheap. In general between $0.25 and $1 each.
I love these old tools because they look real cool, their quality is in general superior to whatever is being made now and most of the time they can still be used.
Most of them are flat so storage is not an issue and if you ride an old bike, chances are they can actually fit most nuts and bolts and more on your bike.
The examples pictured in this post can handle bottom bracket assemblies, pedals and most nuts on older bikes. They can not only be used on the road but in the shop as well.
So keep your eyes open, you just never know what you might find. I like nothing better than collecting old things that can still be used. I figure I get more value for my money than just getting a pretty looking paper weight.
Until next time ride safe and free.