Are you definitely wanting to stick with something small and looks more or less like a cig? If so I'd go with either ego, or a spinner. The spinner is much like an ego twist, but it's much easier to see the numbers on the dial.
VISION Spinner eGo VV : GotVapes.com, E-cigarette Supplies - Atomizers Cartomizers Mods Juice and more I really prefer variable voltage, it really does make such a difference.
If you don't care about size shape etc and want to invest a bit more, I can't say enough good things about my gripper vv.
SMOKtech Gripper VV 510 & 808 : GotVapes.com, E-cigarette Supplies - Atomizers Cartomizers Mods Juice and more a bit smaller than an altoids box, shows the ohms of your juice holder and how much battery power is left and what voltage you're vaping at. It's plastic, but mine has held up great.
If you really don't want to get into vv, then a regular ego is great too, but I would stick with 510. I personally don't like filler cartos, I prefer clearos and my fav hands down is the vivi nova. I've tried some others that have come out since the vivi, but none have beat the vivi for me. Just depends on what you're wanting. The vivi comes in full size and a mini version.