Not all sweat is created equal. In fact, there are two types of sweat, created by two different kinds of glands. The eccrine glands found on the hands, feet, and forehead produce sweat which is 99% water and therefore doesn't offend the nose. The apocrine glands, however, can be found around the groin and the armpits and are to blame for your unique brand of BO.
Depending on the kind of sticky situation you find yourself in, one of these two kinds of glands will start working overtime. Here are some classic sweaty scenarios: