V Lock

Keys are notoriously difficult to align to locks, especially at night.  The V Lock by Junjie Zhang solves this problem by creating a large groove on top of the lock, "funneling" the key to the hole easily.

Aside from being a remarkably intuitive design, it's actually cheaper than a regular lock due to less material being used. 

Source: Yanko Design

Piggyback Plugs

A piggyback plug is a plug that also serves as a socket, as shown below:

With only a slight increase in manufacturing costs, the piggyback plug allows multiple appliances to be plugged in without the need for an extension cord.  This design has been out in Europe and Australia for many years, but has not been put into widespread use.

Source: Drumalarm

Greywater recycling

Current designs of toilets use fresh water for flushing.  Sink Positive is a retrofit sink that can be placed on top of any toilet.  It allows greywater to be used to flush the toilet, maximizing water usage.

This design has been implemented in Japanese homes, as can be seen below:

The mechanism is simple and requires no additional pumps or mechanical materials.  As the diagram shows below shows, the fresh water used to refill the reservoir simply passes through the faucet first before being added to the tank.  The runoff after washing is then used to refill the bowl.

Advantages:
1. Large amounts of water savings
2. Space-saving; a separate sink is not necessary.
3. Toilet leaks are easy to spot. Whereas for conventional toilets, water refilling is done internally, here, any noticeable sink dripping means a leak.

Disadvantages:
1. For the uneducated, it looks like you're using the dirty water from the bowl to wash your hands. 
2. The toilet bowl impedes access to the sink, requiring the user to stoop to use it.
3. The flush button needs to be pressed every time anyone wants his or her hand washed.

The last two issues are easily fixed with a different design, but it will remove the elegance of a marketable retrofit toilet cover.

Source: Sink Positive

Restless Chopsticks

These chopsticks by Mikiya Kobayashi are cleverly designed so the user does not need a separate chopstick rest. Placing them so the indented portion faces upwards prevents the tip from being in contact with the table. The restless chopsticks come neatly packaged in pairs and are available in black, green, red, white or yellow.

Source: Emmohome

Brush and Rinse

This toothbrush concept from Scott Amron can redirect water from a faucet to the user's lips for easy rinsing. This toothbrush has a slight indentation behind the head that redirects water in a stream to the user's mouth, removing the need for rinsing cups or using one's hands to get water for rinsing.

There are two incarnations of the design, though I prefer the one above rather than the second one, if only because of the greater risk of contamination with the tube-type brush.  The best thing about this design is that it adds no cost for manufacturing.

The video of the toothbrush in action can be seen below:

Source: Amron Experimental

KEWB Multifunctional Furniture

The Design of KEWB Multifunctional furniture allows it, with only a few simple moves, to change into many different forms, including, but not limited to the ones shown below.

1. Compact Mode - Packing the entire KEWB furniture into the smallest space possible.

2. Chair and table - With three different recliner positions.

3. Recliner and table - Again with three different recliner positions.

4. Bed + Side table

5. TV Shelf + side table + pouffe / cushions

5. Layered shelf + pouffe / cushions

Furthermore, having multiple copies of KEWB allows the user more combinations of furniture, such as double beds.

Source: KEWB