I believe the correct usage is "whoever" because "for whom" would mean the sentence should have a direct object, which it does not, unless "have" acts upon "one ticket"; does it? Thank you. Matt
A.The correct word here is "whoever," but not for the reason you suggest.
"For who(m)ever would like to use it" is a prepositional phrase. Since "who(m)ever" comes after a preposition, people often feel that it is the object of the preposition and should be "whomever."
However, the object of the preposition is the entire clause, "whoever would like to use it." "Whoever" is the subject of that clause.