Sam's Allspark Shard detailed replica in TF ROTF.
This is a solid model. Metal prints will give it a satisfying weight when being held.
Works well in stainless steel while Silver can show more details. The advantage of silver is it can have a wonderful patina as it age (or you can make a patina with bleach and buff off the reliefs). This will enhance the look of the shard. Might as well become a family heirloom :)
Check out TF AllSpark Shard w/ Hole if you want to use it as a pendant or tie it to a keychain, etc.