Over the years, I have used a variety of Bug Tracking Software. Some of them have been home-grown, but many have been commercial products. The one common factor between all the software I've tried is that none of them really seem to be a good fit with the way I work.
I've been looking at Axosoft OnTime 2005 recently and I think this may be what I've been looking for. Between the multiple versions (Web, Windows and VS.NET), the cool SDK and the customer portal, I don't think it can get much better.
Only time will tell if this is “the” product, but I'm willing to give it a go. :-)