Nikon TC 17

A great extender for the telephoto lenses. Eats a stop of light, but gives a lot more reach and transforms the 70-200mm f/2.8 to a 120-340mm, and add to that the DX factor and the combo in principle a pretty bright 190-540mm. A very easy and even inexpensive way of getting telephoto reach - even though we're not exactly talking a cheap piece of glass!