The Canon EF-S 18-200mm IS zoom is my most-used lens. It may not have the tip-top, best optics. But it's size, weight and zoom range make it the most versatile lens I own and that often trumps image quality - especially when I'm on skis or a bike. And the image quality is really very good - much better than I expected when I bought it.

It's important to note that this is my own person lens. That's why it's so filthy. I am not a good example when it comes to keeping my camera gear clean