Personally I find the Dr Pepper (rum cola) quite good. I haven't tried any of the the others, nor have I felt the need to, since this one seems to be a pretty close match to an actual Dr Pepper flavor.
Some other flavors to consider would be:
Mountain Dew
Tiramisu
Orange Cream (dreamsicle)
Blackberry
Cinnamon Redhots
Toffee
French Vanilla
Gingerbread
Graham Cracker
Key Lime
Lemon/Lime
Malted Milk
Cherry (that doesn't taste like cough syrup!)
Plum
Tangerine
Mandarin Orange
Waffle
Black Sesame Seed (toasted)
Apple Pie
Blueberry Cinnamon Crumble
Boston Cream Pie
French Toast
Irish Cream
Kahlua or Kahlua & Cream
Pralines
Pralines & Cream
Pound Cake
Beer
doughnut
Margarita
Tropical Punch/Fruit Punch
Toasted Almond
Marshmallow
Mangosteen
Butterscotch
Apricot
Citrus Mix (orange,lemon,grapefruit,mandarin orange)
Cookie
Gin
Meringue
Torrone
Red Wine
Vanilla Bourbon
banana cream
Horchata
Lemonade
Pistachio
as you can see there are multitudes of flavors, not currently carried by HC, that could be added if their were sufficient interest.
personally, I find most of your flavorings superior to many others on the market, so I would love for you to expand your product lineup.
The only other comment I have is that some of the names you give your flavorings are a bit too cryptic, and make it hard to determine exactly what the flavor might be. Some examples of this would be-
milk egg (custard?)
italy cheese (cheesecake?)
soda (not champagne, not cola, so what is soda?)
milk mint (?)