I've tried at least a dozen different kinds of cat litter, including most of the ones mentioned in this thread. The one I've settled on is Swheat Scoop Multi-Cat. It's not perfect, but it's the least annoying of all the different ones I've tried. It has no harsh artificial fragrances, it's natural (no chemicals, no clay or silica), the pee clumps are safely flushable if you choose to do so, it doesn't have a lot of dust, the cats like it (very important!), and it doesn't aggravate my cat's asthma/wheezing.

It can be a bit pricey at some stores. The place that seems to have the best price is Target.