Ok--I'll divulge my beauty secret: Retin-A. I began using the gel when, in my late twenties, I suffered from mild and occasional (but nevertheless irritating) cystic acne, a nasty problem that I never experienced as a teen. After being enormously dissatisfied with over-the-counter creams, gels, pads, etc., I tried Retin-A.
A friend of mine had used the stuff for twenty years, and her skin was dewy, clear, and wrinkle-and spot-free. She swore by it. And after using it myself for over three years, I've noticed a significant reduction in acne and sun spots (thankfully, I haven't yet earned my wrinkles). I, like many Asians, are prone to sun spots the way white women are prone to wrinkles, and so I fight relentlessly against them with the zealousness of a perfectionist with tweezers.
Sure, many women lack the patience to deal with the initial negative results: the redness, the peeling, the acne (in reality, the gel pushes all of the skin's impurities to the surface, making your skin look worse temporarily). But after becoming inured to the gel's strong effects, most women will only notice a drastic improvement in their skin's clarity.