I've only tried TFA Papaya, but it is currently one of my favorites! Papaya seems to blend well with any of the tropical fruits.
Also good with rum. I haven't mixed these but have a hunch it would be good with creams and vanillas. Strawberry is another idea (TFA Ripe Strawberry + Capella Sweet Strawberry + TFA Papaya sounds good!). If you pick up the TFA, it is pretty strong stuff! 4% standalone and 1% or less in a mix is good. At 1% it can still dominate, so consider going as low as .5% if you just want an accent. I think very small percentages could be useful to "juice up" some other flavors- I have a hunch adding .1-.5% to cataloupe or other melon flavors would really make those flavors sing (not my cup of tea though- not a melon fan). Hope that helps!