Guild Wars 2

There should be some kind of transmutation stones, that removes the soulbound.

there actually is (when it comes to skins). Transmutate to a white skin to make the skin accoutn bound, then place it in your bank, pick up with another character and transmutate the skin to an item with the right stats.

If it is the stats your after its a bit more complicated, but still doable.
1: Transmutate to a white item to make it account bound
2: place it in your bank and pick up on the other character
3: use a transmutation splitter to undo the transmutation mentioned under 1.

This way you can do it for all items that can be transmuted.