So, my idea is Slime Potion. It is a healing item that I see healing somewhere in the range of 3.5 to 6 hearts. The catch: you can only use it to heal something other than yourself. Tamed Wolves; Creepers; Your Friend in SMP. Yes, I thought up this idea because I think SMP needs a way of players healing players. Here's my design for Crafting:
(pretend the Wool is a Slimeball) So, putting that together would give you one bottle of Slime Potion. It was originally meant to be a spray bottle, but I couldn't think of a way to Craft that without taking too many materials to be worth it. So, I guess you could just pour it on your friend. Either way, this item would allow players to heal other players in SMP. It is still useful in SSP for healing Tamed Wolves, as well.