Such a thing would probably only prevent attacking or blocking but still, there is quite a lot of design scope to cover just in the realms of fair Pacifism like cards that cantrip
Put a nest counter on Twitching Doll
It says whenever Darksteel Splicer or another nontoken Phyrexian enters the battlefield under your control, create X 3/3 colorless Phyrexian Golem artifact creature tokens, where X is the number of opponents you have
Chop Down can take down creatures with a power of four or greater
Prison/stax decks stop your opponent from playing cards and attacking you while gaining incremental advantages over time, be it with lifegain, Treasure tokens, or card draw
That reflects the increased cost of UB products in paper Magic, and since the prize involves physical Magic cards, the entry fee goes up accordingly