I'd love to have moderately priced practice ammo in .257 Roberts (hunting ammo in .257Robts. is moving toward two bucks a shot) and .35 Remington.
Practice ammo in .38 Spl. and .45ACP.
I also agree with other posters' lists (earlthegoat2's post #29, and other posters' suggestions of various revolver ctgs.). I just don't personally shoot (and therefore don't buy) those other calibers at present and don't want to give false weight in your survey to them just because I think that they're cool.
I'd like to see a source of the non-Special .38 S&W ammo, so that we can buy up the neat old revolvers in that caliber which are currently very expensive to feed.