Peach's Crown

Crowns are items appearing many times in the Mario series on top of people's heads, mostly those of royalty.

Princess Peach
The crown of Princess Peach Toadstool is her emblem and a symbol of the Mushroom Kingdom. Toad Guards feature a picture of Peach's crown on their shields in Super Mario Galaxy. Princess Peach is typically seen wearing this crown. In Super Mario RPG: Legend of the Seven Stars, Princess Toadstool looses her crown during her wedding to Booster and Mario has to go find it along with her other accessories. Mario eventually finds the crown on top of Booster's head and gets a kiss from Peach, Booster or Bowser (or Booster kisses Bowser) depending on his speed.

Princess Daisy
Princess Daisy also owns a crown as she is the ruler of Sarasaland. Her crown is orange, much like her dress, with several green-colored jewels, similar to her earings. In Super Mario Sluggers, her team's emblem is her crown surrounded by vines. The crown does not take any prominent roles other than appearing on her head in every game in which she appears.

Other
Many other characters such as Queen Bean, King K. Rool, Wart, Rosalina, Shadow Queen, Princess Shroob, Queen Bee, and Big Bob-omb wear crowns as a symbol of their rule over a certain species and/or location. No crowns other than Peach's and Daisy's make appearances other than on top of their owners heads.

Trivia

 * Bowser wears a golden crown in The Adventures of Super Mario Bros. 3 but his crown never appears anywhere else.