I've found a bug where a hopper will pass an item to a minecart chest through blocks or even air when facing North or West.

To replicate:
Place a minecart chest on a piece of rail.
Place a hopper 2 blocks South or East of the minecart, facing towards it.
Put an item in the hopper.

This works with a block between them or with an air block between, on all types of rail, with chest and hopper minecarts, with and without the rail under the minecart and with the hopper on the same level as the minecart or one block higher (as shown).

This was done first on LAN multiplayer survival, then single player creative, both completely vanilla.