Edison Format · March 2010
Sending a monster to the GY is a cost to activate "One for One".
"One for One" does not target. The monster you Special Summon is chosen at resolution. If you were planning to Special Summon a Level 1 monster from your hand, but no longer have one at effect resolution, you have to Special Summon from your Deck instead (and vice versa).
If there are no Level 1 monsters in your hand or Deck, you cannot activate "One for One".