Here are 50 effects for a magical fountain to use in your D&D campaign. The intention is for them to be neither positive nor negative, but to be interesting. I think 21 is my favorite.
1. Voice sounds like you inhaled too much helium
2. Gender swap!
3. Turn purple
4. You believe you are a character in a role-playing game
5. Any time a magical effect hits you, you give off a burst of fireworks
6. Everything you eat tastes like peppermint
7. You become irresistible to teenagers until the next time you bathe
8. You are unable to recognize your own name
9. Flowers sprout from your ears
10. All your hair falls out
11. You expand like a balloon, with your equipment. You tend to float away if you don't pay attention
12. Your beard immediately grow to two feet long
13. The stars in the heavens are visible to you, even during the day. Even underground. Unless you go too deep, then the stars of the underworld appear to you.
14. Your clothes all disappear. You find them in your backpack, cleaned and neatly folded.
15. All conversation seems to you to be in song, like you're in a musical.
16. Temporarily learn the speech of trees. You feel a mild compulsion to do what they tell you to.
17. You start to glow. No, literally glow.
18. You can touch any piece of cloth and know who wove it
19. Facial features float around surface of face for 1d6 turns, reset to normal after that.
20. You gain a hat. Roll
here.
21. 3d6 extra-dimensional salmon leap out of the fountain, and into a hitherto unknown "salmon portal" in your backpack
22. All of your hair is replaced by steel wire
23. You are polymorphed into yourself. You feel vaguely uncomfortable
24. You think you are communing with your god, but you're actually just talking to yourself
25. You gain the dress and mannerisms of a goth
26. You are sent two minutes into the future
27. Your sense of color is scrambled -- see all colors as a different color
28. Change race -- as in, to/from black, white, 'middle-eastern', etc.
29. Blessed by St. Palmatius, patron of butchers. +1 to rolls to make charcuterie.
30. Become mildly magnetic. Doesn't affect large objects, but nails are attracted to you. +1 to reaction rolls with iron golems
31. A glowing object follows you around and gives you utterly unnecessary advice. Has the voice of your mother. If you're married, save vs. spell or it's the voice of your mother-in-law
32. Become religiously fervent
33. All metal you touch turns to chitin
34. Spirit journey: basically an adventure within the adventure that gives you some great insight. Perhaps only into yourself
35. Voice becomes impressive and booming
36. Ears become relatively smaller
37. You understand you are a character in a role-playing game. Philosophically this changes everything. Practically? Not so much.
38. You can communicate telepathically with one other random member of the party. They must make a saving throw each time or freak out
39. Can speak the language of fish for one week
40. You learn the location of the nearest gem
41. You cannot hear what other people are saying to you. Instead, their words appear above their heads in rebus form
42. You smell stale tobacco wherever you go
43. You smell of stale tobacco wherever you go
44. A minor demon appears on your shoulder and gives bad advice. Disappears if attacked, only to reappear 1d4 rounds later
45. You gain a random tattoo in the small of your back
46. The name of your most recent lover appears tattooed on your arm
47. All beer tastes like wine, and vice versa
48. To you, everyone looks like they are undead -- your party member all look like skeletons and zombies now!
49. You believe you have the head of a fish
50. You gain the ability to measure spices and similar products by hand, exactly
Thanks to the many Google+ peeps who contributed to this!