If I was forced to own one lens that did everything, I guess I'd probably go for the
Tamron 18-270 VC. It goes from a true wideangle (18mm) to a pretty decent long telephoto (270mm), plus it has built in stabilization. It's also compact at just under 4" long when at the 18mm setting. It's not cheap, but for a single lens it does a lot.
The best "bang for the buck" might be the
Tamron 18-250. It's half the price of the 18-270 VC, but it doesn't have image stabilization. I did a full reveiw of it here -
http://www.bobatkins.com/photography/reviews/tamron_18_250_1.html