~を喜ぶ (be pleased about)

The verb 喜ぶ ('be pleased, rejoice') unusually takes を for the source of joy — プレゼントを喜ぶ ('be pleased about a present'), 成功を喜ぶ ('be pleased about the success'). Most emotion verbs take に, so 喜ぶ + を is a marked exception worth noting.