If Sigilyph with the "Toolbox" Ability gets attacked with something that discards a Pokemon Tool who gets to choose which tool gets discarded?
If an attack says to discard a Pokemon Tool it will discard all tools attached to that Pokemon, not just one. So poor Sigilyph would lose all of his tools.
Source: Plasma Blast FAQ (2013-08-15), TPCi Rules Team (2013-08-15)

Relevant cards

Note: All applicable cards may not be listed below.
BW10_41