We love hex nut projects.  Hardware bits are such fun as craft supplies!  Over at i try DIY, Mikko used hex nuts joined with jump rings to create a heart-shaped pendant that would make a great Valentine's Day gift.  If hearts aren't your thing, you could arrange the hex nuts in an endless number of other patterns instead.  For a different look, try using nuts with different finishes, or use colored rings to connect them.  [how to make a hex nut heart pendant]

Project estimate:

• Hex nuts, on hand or $1 and up
• Jump rings, on hand or $1
• Cord or chain, on hand or $1 and up

Total:  Free and up