My current faves are:
Sigma 10-20mm
Sigma 50-500mm aka The Bigma
The bulk of my digital shooting these days is done with these two lenses. A really fine pair of lenses that are supremely usable and provide me with some really nice shots. The only thing I can fault them for is that they are a touch on the cool side with the image rendition. Other than that I don't have any major gripes.
I usually shoot handheld with that lens but often take my tripod (Manfrotto 055 ProB) or monopod (also Manfrotto 679) as it gets heavy just standing around with it. Ideally i'd like to get a gimbal head for it as well to round off a superb setup.
My dream lens would be the newer even bigger Bigma.
I seem to recall hearing about an f/2.8 version of it. IRC it was f/2.8 continuous ! I think with one of those babies, all my problems of shooting the local shipping in low light would be over. But probably the start of my back problems. Would have to start saving for trips to the chiropracter.
Photocite: Move over Bigma, there's a Monster coming.
Oh and the 500-1000mm one mentioned would be really nice to have as well. Mucho bucks tho $$$$$$