I personally use a 5v Saber Touch with a 510 connector and a GLV 5v with a 901 connector. When the XL C-E2 510 Cartomizers come in, I plan on using them on the Saber Touch and GLV with a 510 adapter.
Other than that, I have a red laser pen that I use to drive my dogs and cat nuts.

(Of course, I wouldn't mind having an Artic Laser S3. I would so love to pop my neighbors' tires)