Well, I'm a fan of Lorann's Pina Collada because it works better for me than the ones I've tried from TPA/TFA and Capella. I like a few of their flavors.
I like a number of TPA/TFA's, and a few of Capella's, a number of FA's, a few of the SC's from ECX and VZ.
For new mixers I usually recommend Capella's because they seldom hit levels 7 & 8 which makes it easier to get the flavoring levels figured out.
Note:
TPA/TFA is The Perfumer's Apprentice / The Flavor Apprentice
FA is Flavour Art
SC's are Super Concentrates from EcigExpress and Vaping Zone
Levels 7 & 8 refer to the chart of flavoring levels from my blog on flavoring levels and some silly mixers think it is a good read.
Added this note since we tend to speak in our own "mixer lingo" not because we are exclusive, but because we are lazy type-ers.