I've been using the Linx Hypnos Zero for the last couple of years. It's beautifully engineered and is very small and compact. It's regarded as one of the better pens on the market and I can't fault the battery life and four different temp settings.
It uses either a coiled or ceramic atomiser with a nice glass mouthpiece.
A cheaper option that I've used is also the Grizzly Honey Dab pen which is a little more industrial in its design