If you're ok with the Top Coil thing (wick it right and it won't leak) the Avocado is my favorite. It doesn't quite match the flavor of say my Petri clone it does if I drip as well as have the tank, in other words if you want a flavor shot you can drip on top of the reservoir to fall back on in times you can't drip. Freshly dripped it's right up there with my best flavor setups, without it, it's easily the best non drip I have.
If you want a true RTA the Boreas comes to mind, it's a whopper but it packs the flavor by overloading you with vapor (over being an exaggerated term, not really overwhelming, just very very whelming). It lacks the on the purity side, IE a dripper is getting Coldstone (insert your favorite icecream place here) where the Boreas is getting a whole tub to yourself of storebrand (but with no calories or feeling shitty after eating all that icecream!). If the Boreas is too big and you want a 22mm, the Diablo comes to mind, more compact, meaning smaller builds less vapor production but the flavor is purer and still robust in it's richness, one of my favorite tanks.
Now there's tons out there, but for flavor my favorite is the Avocado followed by the Diablo/Boreas (impossible to decide between them for flavor, though I like the Boreas overall better though I love the form/fit of the Diablo plus it brings out a different flavor). Those would be my three top suggestions.
Now, additional ones I'd feel are worth looking into from either experience(starred *) or word of mouth: Theorem* if you like single coils, Merlin as well for single coil, Moonshot, Limitless, Conqueror, Haze RDTA* (again for single coils), Griffin* (larger 22mm option), Serpent (more MTL), Goblin Mini (more MTL).
Right now I'm vaping my Theorem which has replaced my Haze, but only because it's easier to wick (not to insert a coil though) and looks prettier. I'm far more a flavor chaser than cloud chaser, but I'm happy with my selection (what I listed above plus a couple Petri clones as far as what I use regularly).
