Not much of a sculptor myself (mostly conversion work!), but I found the Royal Sovereign Clay Shapers to be super-useful.These are basically like brushes, but tipped with shaped silicone instead of bristles. Get the black-tipped ones though, as the grey / white tipped are pretty soft. I found the smallest sizes (Size 0) to be the most useful, and last time I checked most decent art shops (both online and brick-and-mortar stores) carry them. Also, Amazon had some over Christmas too I think.
Other than that, some fine dental tools and a couple of sizes of X-Acto blades are all I use really.
For doing rivets on models, fine brass tube or mechanical pencils are often handy too.