Body Boudoir Coochy Rash Free Shave Creme (for sexy skin) is wildly popular and perfect for shaving those delicate areas. Although it doesn't lather at all, it gives a silky shave and truthfully does prevent razor burns and rashes. It comes in a bigger-than-most bottle that will last and last and last. The only down side is that, as far as I know, the only place to get it is the internet or pleasure parties. If you happen to have a boutique near you that carries it please let me know! (available in unscented as well).
At the pharmacy, you can easily get ahold of Bikini Zone Anti-Bumps Shave Gel. This stuff is only available in small tubes but it is extremely gentle on the skin, keeping razor burn and bumps to a minimum. When getting ready for a special date ;-) I save it for my bikini area and use other shave gels on the rest of my body. Also, if your underarms are unusually sensitive I see no reason why you couldn't use it on them.
Although it isn't officially a shave gel my favorite product to shave with is Philosophy Shampoo, Shower Gel, and Bubble Bath. Not only does in come in a dazzling array of delectable fragrances (ie. Raspberry Sorbet, Senorita Margarita, Vanilla Birthday Cake, and their most famous light floral, Amazing Grace) but it is super foamy and gives a tight shave. It comes in a large bottle that will last you forever, so once for ounce it is quite economical. Around the holidays Philosophy comes out with some really fun gift sets and sell my most favorite "flavor" of all: GingerBread Man, a fresh and spicy ginger scent.
all products reviewed were either bought or sampled by me. And product pictures were stolen from the link's website. I am not financially compensated for my reviews