Seal, "Kiss from a Rose" from "Batman Forever"
As the years wear on, "Batman Forever" is looking more and more like the least memorable Batman entry in the entire pantheon, largely because of its blandness and naked eagerness to please (by comparison, "Batman & Robin" is a more enjoyable mess), but Seal's "Kiss from a Rose" is still stuck in our heads. Originally released in 1994 as part of Seal's second self-titled album (known as Seal II by people who like to talk about this kind of thing), it was re-released for the "Batman Forever" soundtrack and promptly blew up. It's woozy romanticism and darkly tinged feel were supposed to evoke the relationship between Val Kilmer's Bruce Wayne and Nicole Kidman's Chase Meridian, originally intended to play over a scene where those two get it on. It didn't end up with that scene but rather was saved for the end credits, which is for the best anyway because you can't help but sing along really, really loudly.
Prince, "Partyman" and "Trust" from "Batman"
"Partyman" and "Trust" are two Prince songs that are actually used in the movie, and they're used marvelously. "Partyman" accompanies a scene where the Joker, in one of the more bizarre and intangible plot threads of the movie, decides to assert himself as some kind of art world deconstructionist, going to a Gotham museum and garishly painting over priceless paintings and sculptures. The scene doesn't make a tremendous amount of sense, but at least with the Prince song, it has a certain amount of bounce (also the idea that one of the Joker's henchmen is being brought along simply to hold a boom box is sort of amazing). The second song, inspired by the Joker's line "Hubba-hubba-hubba-hubba, who do you trust?" plays over a sequence where the Joker rolls through town on a parade float, passing out money, while plotting to kill the citizens of Gotham with giant balloons filled with poison gas (no, this doesn't make much sense either). This song is not only a really great party jam and captures the frenzied mood of the sequence, but is a testament to Prince's rapid-fire genius -- the "Batman" album was made in six weeks, sometimes incorporating demos or previously recorded songs, modified to fit the super-heroic purposes.