Unlike every other item class in the game, potions do not give the "A <foo> only works in connection with arrows" (where <foo> is sling/bow/crossbow) message when attempting to shoot them from a missile weapon. This means that it is possible to shoot potions with a bow, crossbow, or sling.

The main benefit to this is that this allow the range of missile-fired potions to be increased dramatically. Normally, a thrown potion goes 3 squares. My level 50 archer can fire a potion of blindness from one end of the board to the other. Presumably other missile effects like to-hit and to-damage also seem to apply, but potions don't, AFAIK, do any damage anyway.

How to trigger:

-Remove all missile weapons and ammo.
-Equip a potion in the missile slot.
-Equip a bow, crossbow, or sling.
-Shoot as normal.

The same method can be used to fire gems from a sling (but not a bow or crossbow). This may be intentional, but I'd doubt it. Gems shot from a sling gain all damage bonuses, AFAIK, and gems of fire shot from a sling still explode as normal.