Contact lens holders (especially those with screw on caps) are pretty useful, albiet sometimes bulky.
You can put just about anything in there you need. For instance...
-Vasoline
For cotton to make tinder, for chapped lips, whatever
-Magnesium shavings
Why shave in the field and dull your knife? Especially when it's freakin cold and you can't feel your fingers. Go ahead and shave a bunch of magnesium before you need it, stick the shavings in the contact lens case to keep the shavings together, and use as needed when you get to the field.
-Ferrocium rod shavings
Yep, you can shave this too (carefully!), and put some powder in with the magnesium or keep it seperate.
Can't think of anything else to put in there off hand, but I'm sure there are other possibilities.