In Steve Jackson Games' In Nomine, Demon Princes are powerful Word-attuned demons, the counterpart of the Archangels. There are more DPs than Archangels, as Hell prefers quantity to quality, but they are still powerful by any yardstick. Some of the major DPs are:

Baal, Prince of the War (as opposed to Michael, Archangel of War - Baal's power is derived from the conflict between Heaven and Hell only)
Belial, Prince of Fire
Kobal, Prince of Dark Humor
Kronos, Prince of Fate (the dark mirror of Yves, Archangel of Destiny)
Lilith, Princess of Freedom (she isn't actually a demon, and her Word isn't nearly as nice and pure as you might think)
Vapula, Prince of Technology
Valefor, Prince of Thieft

Above them all, of course, is Lucifer, former Archangel of Light, now Prince of Darkness and all-around Not Nice Guy.