+1
I also like to keep a $50 hidden in my wallet and have used it on more than one occasion.

The biggest reason I like cash is that I find using cash is the best way to teach my children how to be fiscally responsible. Hoarding cash made from lemonade sales & mowing yards and having something to physically put into a piggy bank. Counting out the piggy bank every once in awhile to see how much they have and then adding some interest from "bank of dad" to emphasize the value of saving. Heading to Toys-R-Us for a splurge every once in a while.

All of these, IMHO, are priceless forms of education for the future that using cash enables and the use of plastic just cannot replicate.