Lyrical displays your iTunes lyrics and various song information like artwork, artist, and song name. It even lets you control the playback, sound, and set ratings for the song, right from the Notification Center! This is incredibly useful if you are using multiple apps and you just don't want to switch to iTunes.
You can also choose to view or hide the current song's lyrics. You can toggle lyrics with just a click, and Lyrical will elegantly expand and collapse to fit the song lyrics.