For those who've never played Pokemon games the 'Rare Candy' item could be used on any of your creatures to give it all the experience points required to reach the next level. When using one they would then be treated more or less the same as any other creature who just dinged (gain new abilities, etc).
I for one would like to see a version of this in WoW. There could be a set of them, purchasable with Justice Points, that you could then use on the character that earned them or mail to other characters to use.
Level between 1 and 60: 250 Justice Points per item (15000 to skip all of Vanilla)
Level between 60 and 70: 500 Justice Points per item (5000 to skip all of TBC)
Level between 70 and 85: 750 Justice Points per item (7500 to skip all of WotLK, 3750 to skip Cata)
Total for 1-85: 31250 Justice Points, not exactly a 'small' number but it sounds about right to me.
Edit 1: I wouldn't expect Blizzard to introduce an item for MoP until the next expansion is released, but I'd then guess it would be 1000 Justice Point per item.
Edit 2: I'm a little uncertain about the best way to implement honor points, as they can be earned far more early by characters. Perhaps they could only be purchased by characters high enough level to earn justice points from dungeons (or maybe even max level only)