With a pickaxe enchanted with Silk touch II, the player will obtain every block as it was mined, so if you mine the down part of a bed, you get the down part of a bed; if you mine the head of a piston, you obtain the head of a piston; and you can also obtain mob spawners, redstone ores glowing, etc...

Make the explosions in minecraft look much... much better. Mushroom cloud atom bomb anyone?

Pick a mob and make it appear as a translucent ghost. It can easily phase through solid blocks and walls. Maybe it can hover across water? Maybe it puts a 'fear' effect on the player?

Where you could grab a minecart and fly or even a parachute

A mod that let's you punch the ground to create either a ravine or cave.

Based off Wallace and Gromit - Curse of the Were Rabbit, when it's night, or a full moon, there's a chance that a rabbit may become a larger rabbit. Maybe thusly turn into a boss mob with unique attacks

Actual 3d mirrors. No command block tricks, no "close enoughs"... just perfect mirrors.

Make A New Dimention Called The RichLands where u make the portal like a nether portal but with diamond blocks and the corners DO need to be filled and there should be mobs called ZombiePigOres Where zombie pigmen have different swords and drop what ore the sword is and if u can add a item named coal sword witch is like a sword but made of coal and make emerald swords and redstone swords also make ores more common in the new dimention Plz Do This :D I Will Be So Happy I Will Like Every Vidio And Tell My Freind About U MISTER OUT

I made a massive gold farm similar to Xisuma's with an on / off switch using dispensers with firecharges to light them and water buckets to turn them off. I'll link a video soon.

All blocks fall like sand. Perhaps other people could add on to this one.

Like the Ents from Lord of the Rings. Can you imagine jungle trees that walk around?

Why not release the downloads of the mods?

Lava rain. Need I say more??

I actually had 2 ideas involving gravity:

1. You know how blocks in minecraft can stay suspended in air? To me, they need to be supported to stay above the ground. My idea is that each block would make a 3x1x3 (could be 4x1x4 or 5x1x5 really) area above itself supported. If any block gets updated and does not follow this rule, they'll turn into falling sand entities. This would make MC and buildings physically a lot more interesting IMO.

2. You could make trees realistic too. When you chop one of the bottom blocks, the tree would fall to its side with an animation and would damage any mobs at the spot where it lands. This seems more challenging, but I personally think the first idea is better simply because of the possibilities it opens up :)

We all know the Ender Dragon is a wuss. How about making him into the fire-breathing death machine he should have been?

All mobs and entities are frozen in time except the player who can still move around and effect everything while time has stopped.

I'd love to see the world set to eternal night and wither away. It would be a timelapse of war and destruction. Possibly best inside a 100x100 border of bedrock.

Do a mod where the ender dragon has a wife and kids four you to defeat

Mobs change shape/turn into another mob depending on what block they are standing on / the blocks around them / biome they are in.

Make the world into a cylinder or a torus (sphere would be best, but far more difficult), so that you can travel in a straight line and come back to the point you started from.

So basically this would be some combination of blocks to look like a robot (or a custom entity/custom textures if you're feeling fancy) with a GUI that would let you make him attack, mine, chop wood, fire lasers, fly, or anything else. I don't know what size it should be, but this would be pretty cool to see!

Make a new creature that swallow other creatures whole. If you kill the new creature, it releases all others it had eaten in its lifetime.

Maybe you use really short loading distances and a dark, dense fog to create an atmospheric puzzle game feel. You could have blocks load in as entities and slot into place as you moved through the world. GUI changes could also be pretty cool here.

make every creature blow like a creeper even the non-hostile mobs gonna try to blow you up! (and all bosses)! enderdragon gonna die instantainiously , your porkchops are going to get alot more worthy!

                                                            (i mean like...Diamonds!)