I run a small minecraft server where I occasionally play obsessively. As such, I have come up with a few things I–at one time–wished was in the game.
Note: these may not be good ideas.
Quieter pistons (a new block, added with some kind of new drop/farmable item to quiet them).
New weapons, along with using iron as a handle to increase durability.
There should be more random structures, but with less point to them.
Entrances to abandoned mineshafts/strongholds.
The sponge block should be re-utilized as a marsh block for swamps. Grass doesn't make sense.
A somewhat expensive way to clear an enchantment from a weapon.
Enchantments for hoes, fishing rods, scissors.
An enchantment to mine in a 3x3 grid extending from the central block actually mined. Should be very rare, and should hiccup on ores.
A pickaxe enchantment so it can act as the perfect tool for any block and not take double damage for harvesting the wrong block.
Should be very rare, shouldn't be combined with any other enchantment.
The deer could just drop antlers, and depending on the age of the deer, the antler would be bigger, hangable on walls. Not farmable (meaning you can't tame them/force procreation[perhaps they die in captivity]), only huntable.
Mummys, snakes, frogs, birds. Each with more drops, each for potions, and other functions.
Only in swamps, short 1x1 brownish creatures live in small huts, passive, but like Zombie Pigmen.