I hate door locks
The lock and keys are an important necessity for residential security. The usual type of lock on an apartment door is a bit messy and needs to be improved. The major fault being, needing to hold the key in a specific type of orientation and then precisely inserting it into the keyhole. This makes it difficult to easily open the door, especially in the dark.
There are plenty of products available in the market that solve these issues, but these products costlier and not easily available. a few examples being, smart card lock, tele-lock, code lock, double sided key lock, etc. Even replacing or making a copy of the keys require special services.
Hence a simple solution would be to have a double sided key with a larger holding end, and having a conical shape surrounding the keyhole. This would make it easy to slide the key into the lock without caring about the key's orientation. highlighting the keyhole area would also be helpful to locate it in dark.
These are fairly small improvements will not substantially increase the cost of manufacturing, would still be easy to replace or remake the keys and would make user's experience a bit more satisfactory.