I have a few handheld computers; ok, 1, 2...5. That counts as a few, right? In addition, I've been going to more and more meetings at work with their laptop (I swear I'm not that important) and detest using the trackpad. I have a couple of mini mice, but with my desktops at home and a workstation for when I work from home, I have more mice than computers.
Given my obsession with miniatures, there are a bunch of tiny mice out there and even some super tiny trackballs. Occasionally, when surfing the interwebs, I do things like search for "smallest _______". One day in my searches, I looked for the smallest mouse and found the Z-Nano Optical Mouse. Initially, it was impossible to find to purchase, but fortunately Amazon and a couple other places have it now. It's slightly larger than my finger and you "left-click" by pressing forward and "right-click" by pressing backwards.
It's not too great for gaming, but it serves its purpose and doesn't take up much space. It rarely gets tangled on itself as there's a magnet to connect the usb connection to the mouse. Additionally, it's a wonderful way to break up awkward silences in a meeting when you take it out of your bag. The best part it doesn't add bulk to tiny clutches when I'm carrying one of my handhelds.