Well, instead of "What's in YOUR wallet?" I'm answering the question "What's in your PURSE?"
I will use the term "purse" loosely, as my purse is usually more of a diaper bag or tote bag of some sort. My purse is usually fairly minimal with its contents. My wallet is a must have. In addition to my wallet, I typically carry some lip gloss or chap stick of some sort. I always have my phone. If I'm just taking a normal outing to the store or somewhere local, there will usually be two diapers and a travel bag of baby wipes. I try to always have a pen with me also. Oh, and a snack container of Cheerios are a definite must, especially if we're going to be out at a restaurant.
See, not much to it is there? I'm not your typical "everything but the kitchen sink in my purse" type of gal. When I'm traveling, I do carry a lot more in my diaper bag/purse. I like to have my Kindle, extra clothes for Tristan, napkins, additional snacks...pretty much anything I can fit in the bag!