What about
Darksteel Mutation? combined with your commander it would be a very potent card to shut down your opponents commanders.
Besides that,
Crush Contraband and
Disenchant could be useful against your opponents artifacts/enchantments.
If you want to troll your playgroup, attach
Custody Battle to a opponents commander or important creature. It usually plays musical chairs then.
![Wink ;)](https://deckstats.net/forum/Smileys/default/wink.gif)
I've just checked,
Kithkin Armor and
Flamespeaker's Will could also be interesting because of their sacrifice effect. Since you get them back with your commander, you could abuse them.
/edit: if sacrifice is a problem in your playgroup,
Assault Suit could help.