I’ll start. My ideas are as follows:
Balimora: drinking from the fountain inspires a chaotic personality, so whichever personality trait is most prominent in the drinker is suddenly made much more prominent.
Ebenguard: drinking from this fountain centers a person, making them calmer and more even-keeled.
Thornmouth: drinking from this fountain confers a drastically increased knowledge of a single topic, for a limited time. The topic is whatever the drinker was thinking of at the time.
Flinterforge: drinking from this fountain results in a flash of creative genius the likes of which none have ever experienced. The drinker will suddenly be inspired to create a master work of epic proportions.
Weatherwatch: drinking from this fountain allows one to visualize perfectly any location on Earth or beyond. Afterwards, the drinker is struck with the sudden desire to visit that location.
Gossmere: drinking from this fountain allows one to party all night. A single drink offers the energy one needs to dance to the beat of the common drum incessantly for the next 8 hours. At least.