As many of you know, Minecraft 1.8 will probably be the biggest update ever! So, it stands to reason that there should be bosses!
GIANT Mabye, in the upcoming NPC Village thing, there could be a very small chance of a Giant spawning in it and attempt to kill its elder by destroying the town. If saved, prehaps the elder would give you a magical picaxe or some other over-powered magic item of mass destruction.
UltraCreeper A creeper that doesn't explode, but rather shoots lightning and spawns normal creeper. 10x as large as a normal creeper. Appears in certain ruins. When killed, blows up the entire island/chunk of a continent 5 minutes after death. After explosion, reveals chest containing TNT and lightning arrows or something.
By