In Munchkin (or any of its various sets) the rules say that "You can discard a Class card at any time, even in combat: "I don't want to be a wizard anymore." When you discard a Class card, you become classless until you play another Class card." It also says the same thing for Races, Accents, etc. for the various game sets.
This wording suggests that the intent is that you can discard an "in play" Class at any time, but it isn't clear about such cards in the player's hand. I would prefer to discard the extra Elf card in my hand so that my opponent doesn't get it during the Charity phase. Can I discard the card rather than give it away?
Note: The rules I am using are the most current rules from the 1st Edition, 23rd printing of Munchkin published May 2012.