I use EMDCC's most of the time, which are very large cartomizers.
But those aren't good for testing new flavors - you don't want to put 4 or 5ml of fluid into one and then find out you don't like the flavor. It wastes all that fluid, plus now your EMDCC is full of juice you don't like.
So I bought an atomizer just for dripping. I was ordering juice from Alien Visions (Boba's Bounty) and just got whatever atomizer they were selling. I already had a drip tip that I wasn't using, but when the atomizer came in, I didn't need the drip tip - that particular atomizer has it's own little cap sort of thing that you can remove, drip, the pop it back in.
Lately, I've also been using the atomizer to drip a higher nic juice right after I eat. That was the one time that I get cravings for a cig, and by dripping a higher nic juice than I normally vape, I've been able to kill those cravings and get off the cigs.