Tampers & Tools - Czech Pipe Tool
Cheap and cheerful!
Really this is the only pipe tool you'll ever need. But buy a half dozen of them (which is less costly than buying even a single moderately priced fancier tool). I have one in the car, one on my keychain, a couple lying around the house, and one in the drawer I keep my tobacco tins in. I broke the "foot" off the tamper on one of them by trying to use it to open a fresh tobacco tin ... but that was just me being stupid (I should have used a coin as you're supposed to). Seriously, don't think about this -- buy a handful of them.