Lindt is good. I generally prefer 70% dark.
I have two favourites, but they may be a little parochial (UK-based) for most of you guys? There's a brand here called Green & Blacks -- it's available in all supermarkets now. Their white chocolate is to die for. Which is weird because I can't stand white chocolate normally, but this stuff must have crack in it or something. It has little dark flecks of vanilla pod in it which you can see.
My other favourite is only really available at Christmas time -- Terry's Plain Chocolate Orange. OK, it's not a bar, it's a chocolate ball which you bang on a hard surface and it separates into little chocolate orange segments, just like a real orange.
Terry's Chocolate Orange - Wikipedia, the free encyclopedia
Green and Black's Global