Mindslicer

When Mindslicer dies, each player discards their hand.

Painful Quandary

Whenever an opponent casts a spell, that player loses 5 life unless they discard a card.

Duress

Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.

Tinybones, Bauble Burglar

Whenever an opponent discards a card, exile it from their graveyard with a stash counter on it.
During your turn, you may play cards you don't own with stash counters on them from exile, and mana of any type can be spent to cast those spells.
{3}{B}, {T}: Each opponent discards a card. Activate only as a sorcery.

Pilfer

Target opponent reveals their hand. You choose a nonland card from it. That player discards that card.