You can only banish as a cost a Normal Trap Card from your Graveyard whose activation timing is correct.[1]
If you banish as a cost a Normal Trap Card from your Graveyard that targets, then you choose an appropriate target for that Normal Trap Card when the effect of "Junk Collector" is activated.[1]
Since the effect of "Junk Collector" does not activate the banished Normal Trap Card, you do not pay the cost required to activate that Normal Trap Card.[1]
Q&A Rulings
Q: Does the effect of a Trap Card which is activated by "Junk Collector" affect "Elemental Hero Wildheart"?
Q: Can the effect of "Junk Collector" be activated by banishing "Fake Trap"?
A: The effect of "Junk Collector" cannot be activated by banishing "Fake Trap", since you cannot apply the effect "destroy this card instead" of "Fake Trap".[7]
Q: If "Junk Collector" is the only monster on the field, then can you activate its effect by banishing "Reinforcements"?
A: If "Junk Collector" is the only monster on the field, then you cannot activate its effect by banishing "Reinforcements", since there would be no monsters on the field to be targeted by the ATK-increasing effect.[8]
Q: Can the effect of "Junk Collector" be activated by banishing "Ceasefire" or "Torrential Tribute"?
A: If "Junk Collector" is the only monster on the field, then you cannot activate its effect by banishing "Ceasefire", since there would be no monsters on the field after activation, so the damage-inflicting effect cannot be applied.[9]
Q: Can the effect of "Junk Collector" be activated by banishing "Ceasefire" or "Torrential Tribute"?
A: If "Junk Collector" is Summoned and is the only monster on the field, then you cannot activate its effect by banishing "Torrential Tribute", since there would be no monsters on the field after activation, so the effect which destroys monsters cannot be applied.[10]
Q: Can the effect of "Junk Collector" be activated by banishing "Treacherous Trap Hole" or "Pineapple Blast"?
Q: Can the effect of "Junk Collector" be activated by banishing "Treacherous Trap Hole" or "Pineapple Blast"?
A: If "Junk Collector" is Summoned while you control no other monsters and your opponent controls 1 monster, you cannot activate its effect by banishing "Pineapple Blast".[12]
Q: Can the effect of "Junk Collector" be activated by banishing "Kunai with Chain"?
A: The effect of "Junk Collector" cannot be activated by banishing "Blast with Chain" or "Metalmorph". The effect of "Junk Collector" can be activated by banishing "Kunai with Chain", but you can only apply the effect which changes an attacking monster to Defense Position when an opponent's monster declares an attack. You cannot apply the effect which equips it to a monster on your side of the field.[13]
A: "The Six Shinobi" cannot be activated unless you have 6 "Six Samurai" monsters with different Attributes on your field. Therefore, it is not possible to banish "The Six Shinobi" when activating the effect of "Junk Collector".[14]