Inspired by http://www.gamesas.com/topic/1409238-how-to-keep-objects-in-display-cases/ and some of my experience, I decided to start this topic for everyone to share their experience about how different objects behave when dropped and moved around. I hope this topic will be useful and I encourage everyone to share their remarks - I'll be incorporating them into this post as often as I can.
---------------------------------------------------------------------------------------------------------------------------------------
Most posters already know that if you want to place any object in your Dragonborn's house, you have to first drop it on the floor, leave the house, come back and only then pick it up and (painstakingly) put it where you want - otherwise all your work will be for nothing and the object will end up where you first dropped it. There are, however, a few exceptions from this rule:

"Cooperative" objects - you can drop them and then put them where you want - they will remain there.
Butter (if I recall correcctly - I'm actually not 100% sure about this one)
Centurion dynamo core
Deathbell
Mountain flowers

Problematic objects
Essence extractor - can dissappear when dropped
Ghostblade - can dissappear when dropped
Glowing crystal shard - after dropping it and leaving the cell, you can't pick it up and manipulate it; you can only take it back into your inventory


I know it's not much for now, but hopefully as I do some more home decorating and with everyone's help, these lists will grow