The classic game of marbles, in a pocket-sized portable form.
Nostalgia is the current marketing trend and apparently selling well. Make your own bit of nostalgia (and play with it when the Internet is down) with this Instructable!
Step 1: Obtain Marbles
Who hasn't played with marbles in some form or another? Dig them out of your closet or your parents' attic. Barring that, marbles are readily available in sets or a la carte in many toy or craft stores. They shouldn't cost more than ten cents each. A shooter is helpful and may run you thirty cents or more.
An Altoids tin will comfortably hold 18 standard-size marbles. Unfortunately, a shooter is too big! We'll have to work around that.
Step 2: Find some rules
Since there are many variations on the standard marbles game, I'm not going to put them up here. Rediscover your favorite game and print/write out the rules for anyone you may play with who is not familiar with that game (or marbles in general!). Tape them to the inside of the top of your Altoids tin. A general rule of thumb for your rule sheet is business-card size or less.
Here's a site with some different games: http://landofmarbles.com/marbles-play.html
Step 3: Line the tin
Line the Altoids tin with some thin foam so that the marbles don't make too much of a racket. Alternately, you could cut out harder packing foam for a precise fit.
Step 4: Finished!
Put it all together an voila! Pocket marbles!
Step 5: Bonus: Prescription Marbles
I also found that a small medicine bottle from the drug store will hold a shooter and four regular marbles, or six regular marbles by themselves!