Vamo Stainless steel vari volt vari wattage 18650, $50. LOVE IT! I'd recommend a vamo to anyone new or seasoned. It's big and heavy but with a carto tank I have a perfect vape all day and night. I haven't tried 18350 because the size isn't a real issue for me.
epower 14650 is a good modular design for 3.7v but variable wattage is where it's at.
5v usb passthrough, but I don't use it now that I have my vamo.
306 and 510 are ok for dripping but I really love an 801 atty for tasting flavors I mix. I mix 100%vg because I have no interest in throat hit.