Hey there Boo, I thought you were (already) nuts!. Just kidding of course...

The Alesis Nanoverb is a great little box which I used to take along for my vocals (before going the 'built in' vocal efx arranger route). There really is NO right efx type setting to use. I would just experiment with different presets/levels and find the one that suits 'your' fancy. My personal favs seem to be the vocal plates.

Just remember, that for jazz stuff, you want to keep the efx to a level which isn'nt outwardly noticeable. I typically start with the efx OFF, and SLOWLY turn it up just enough to enhance the voice (or instrument) but not overpower.