This is a tough one!  The lens I use the most is actually not my favorite...but is more versatile for everyday carry.  That everyday lens is a mid-priced Sigma, 18-130mm zoom on my D70.  A better lens and with VR is the 18-200 Nikon lens I got with the D200.  Neither is lower than f/3.5 but both suit my purpose overall for zoom.

My favorite? A Sigma 50mm prime macro, f/2.8.  Second place is a Sigma 30mm f/1.4 which gives close to a 50mm crop in either the D70 or D200.  I love the 30mm because of the crop view ; despite its shorter focal length, aberations are not a problem overall and less than in either of the zooms at similar focal length.

My least favorite is the Nikon lens that came with the D70 kit.  Can't even remember what focal length range it has.  I haven't  used it enough to really say if it is a good lens or not! That is simply because I had zooms to do more.

A last choice and quite nice is Sigma 100-300mm zoom, f/3.5. This filled a place Nikon could not fill and certainly not at a close price.  Sure, not as fast a light gatherer as some higher priced lenses but 3.5 serves my purpose. This one is 3.5 across the range, sharp as tack and internal focus.  I like this one very much.  However, I don't often opt to everyday carry of that full frame lens due to weight and size.   My bunnie in the city pics were shot with the Sigma.

Sorry, hard to pick a real favorite..so much depends on the days shooting.  Again, my most used lens is the Sigma 18-130 used on the D70, my everyday carry cam.   The "favorite" macro Sigma comes in second in use and is always with me in the bag.  The macro also does a good job as a prime lens with its approximate 75mm crop for people shots, etc.

My budget does not allow the high priced primes from Nikon. That is simple enough. Not to say I don't want one!

Enough confusion...now I am confused about these lenses. LOL      TomDart.