Thoughtseize It may cost you two life on top of the one mana, but Thoughtseize is one of the most effective reveal/discard combos available
How Do Tribal Spells Work
Blue can be oppressive to fight through for Red, Boros, or Gruul decks
Timetwister has been omitted from the list, mainly because its not quite as ubiquitous as the rest, and not every deck would want to play it if it could
These two are a bit less powerful than their white, blue, and black counterparts, but they'll absolutely see play with Ashling and the backup commander, Mass of MysteriesMass of Mysteries, as well as the aforementioned Horde of Notions
Otherwise, its still a great way to use that extra two mana for about a 25% chance of success