I (and Mel) think it would be really fun to make a potion that has the properties of the Babbling Potion and Truth potions...so people end up just babbling things...

here are some ideas:
1. Babbling Truth
2. One that gives temporary metamorphmagus powers to the drinker - (like polyjuice but only able to change one feature per dram of potion)
3. a 'drive' changing potion, so it changes the drinkers view of things so it could make a very intelligence driven person think more in a "what is brave? what is right?" mentality, sort of as a means to understand what drives members of other houses.