Lange Nacht der Münchner Museen 2006: an event in which many museums and galleries in Munich stay open late for a night. A ticket gets you in free everywhere plus onto public transit.
24 Hour I Amsterdam Card. Gets you into a bunch of museums free, plus public transit, plus discounts at restaurants and other places.
Ticket to the Rijks Museum in Amsterdam. Price on ticket is 0 because I used the I Amsterdam card to get in.
Ticket to the Van Gogh Museum in Amsterdam. Got in free with the I Amsterdam card.