A comment in another thread got me to thinking.  I have a huge number of recipes that I've collected off of the net, from friends and family and from various cookbooks.  I've never actually baked/tested most of those recipes because it just seems easier to modify the trusted/tried and true ones I have.  For example, my vanilla cake recipe has become my go to for lemon, orange, lime, red velvet (using the lorann emulsion), lemon basil even though I have a multitude of recipes for lemon, and orange cakes that I've never tried.  Or I have a white white cake recipe that serves for my rainbow, confetti and cherry chip cakes as well as almond cake. Though I do plan to try From Scratch's white cake recipe tomorrow, but that's more because I want to try the yellow version with the egg yolks because I don't have a good yellow recipe.  I'll also be trying my white recipe with just the yolks to see how it turns out as a yellow cake.  So, how many go to recipes do you have?  Mine are:

Dark chocolate (similar to the Hershey one)

Vanilla (becomes lemon, lemon basil, orange, lime, red velvet

White (rainbow, confetti, cherry chip)

Carrot

Maple

Peanut butter

I love recipes, but for the business I have my go to recipes and don't vary from them.  I tested out a bunch in the beginning and settled on my favorites for the business.  I have:

vanilla, which is used for citrus, chai spice, espresso, dalmation (chocolate chunk), and banana

chocolate, which I use for chocolate and chocolate stout

carrot

red velvet

I don't offer a white cake because I don't care for them, and my vanilla butter cake is not deeply yellow.  Plus so many people are used to a white cake mix cake and not a true yolk-less sponge and they don't understand why the texture isn't like the cake from the grocery store.  No one has ever missed white cake here... LOL.  Most of the interesting flavor combos come from the fillings more than the cake layers, and by adding simple syrup washes or soaking with liquors.

I have other cake recipes that I like to use for family events and such, but for the business I like to keep it simple.  I know all of the recipes by heart with all of the variations and I don't have to think about it after almost 6 years... LOL. 

I have just a few that I change up, too...

Pure White morphs into White on White Chocolate, White Caramel, Amaretto and Gingered Peach and the Raspberry for my Lemon Raspberry Swirl

Deep Dark Chocolate to Swiss Mocha, Walnut Fudge

Golden Yellow (a classic butter cake) becomes Lemon, Sugar 'n' Spice, Pumpkin Spice, Peanut Butter, Egg nog

Carrot, with or without raisins, walnuts and coconut

German Chocolate