Iolite Wispr 2

Unlike the others here, the Wispr 2 doesn't have a battery and runs on butane. Once it's fueled, you simply click a side lever to engage the 400-degree heating element. While they bemoaned having to add fuel, testers thought the Wispr 2 more often than not produced a strong vapor. They also loved its compact, easily-pocketable shape and foldable silicone pipe. [$170; iolite.com]