The RDA (Rebuildable Drip Atomizer), a rebuildable dripping tank which requires users to manullay drop ejuice straight on the coilds & wick inside the tank. Once you drip your juice inside, vape it off (two or three puffs), then drip some more.
An additional advantage with this is that you can change up your liquids more frequently, but for some carrying around bottles may be a pain - RTAs may be a better choice.