Melon

Melons are a planned and confirmed feature to be added to Minecraft's 1.8 Adventure Update.

Behavior
Melons will have a central stem that slowly grows until it reaches its maximum size, at which point the melon will randomly spawn a fruit next to it if there isn't one already there.

History
Melons were first revealed in an IGN interview with Notch.

On the Getsatisfaction.com complete ideas for the Ideas section, it has stated that Watermelons will be implemented.