1) As a Bike Speedometer: After his bike speedometer broke, Instructables user Alexdlp decided to make an upgraded replacement using an Altoids tin.
2) As Mini Speakers: You'll need two Altoids tins if you want to follow Ken Kirkpatrick's, winner of ReadyMade's MacGyver Challenge, instructions and create your own set of mini speakers using a pair of old headphones.
3) As a Solar USB Charger: Follow Instructables user JoshuaZimmerman's instructions to make your own solar powered USB charger. Prefer to charge your iPhone instead? No sweat, he has instructions for that project as well!
5) As a 1/8" Stereo Mixer: Ever have not quite enough aux inputs in your stereo? Instructables user Richfiddler11 had the same problem, which he solved by creating this 1/8" stereo mixer out of the ever so humble Altoids tin.
What is the most interesting Altoids project you've spotted?
(Image credit as linked above)