Cleric, Druid – Cantrip – Guidance
Casting Time: 1 Action
Components: V, S
Duration: 1 Minute
You touch one willing creature. Once before the spell ends, the target can roll a d4 and add the number rolled to one ability check of its choice. It can roll the die before or after making the ability check. The spell then ends.
My Comments: At the tables I've been playing we house-ruled a limit on the number of cantrips casters have at their disposal and this is one of those spells that totally justifies it. If a cleric has unlimited cantrips, the DM might as well just assume every single non-combat skill gets an extra d4 added. In combat, there would be a good reason for the cleric not to waste a whole action on it, but outside combat? There just isn't any reason not to spam this spell for every single ability roll in your party.
A DM could insist that the cleric announce it each time and give the evil laugh on the times they forget, but that's almost more annoying than just letting them have it.
All that being said, there are limitations that a DM can work with:
One is that it requires concentration, so no other concentration spells can be cast while this one is in effect. Not a big deal though, because it's usually cast right be the ability check is rolled, so no concentration is needed.
The other is more roleplaying; it requires the character to speak and wiggle their fingers, so if the other parties involved may catch on that magic is involved.
Cleric- "In the name of the great god Harvey, I humbly grant you greater ability to haggle with this shopkeeper."
Shopkeeper - "Wot's that? Wot did your friend there just say? Wot are you trying to pull here?"
Cleric - "In the name of the great god Harvey, I humbly grant you greater ability to move stealthily."
Guard1 - "Hoy Bob, did you hear somebody mumblin' over there in the shadows?"
Rogue - "...thanks a lot."
The obvious quick note: This spells works with Ability Checks, not Saving Throws or Attacks. This question comes up a lot, so I thought I would mention it.
(The image below links to a survey on Die Hard Dice about d4, so go give them your thoughts and then get one of their cool dice sets so that the next time you roll your solid metal d4 people hear it.)