Chris W wrote:
If you were about to go on an IFR flight, and for some unknown,
hypothetical reason you had to pick one instrument in the standard six
pack that you could not use, which one would it be?

You do err, for as the CFI-I, I am the one who gets to pick which of
those instruments it will be, and I am liable to pick more than one of
them. BWOOWOOHAHAHAHAHAA!