Immobilize player by stopping them from putting creatures out, having creatures tapped, or enchanted to not untap, or use combos. Not really my style to play, I would feel guilty all the time and the other player would likely get frustrated and have less fun.
Combos:
Curse of Misfortunes/Overwhelming Splendor;
Conjurer's Closet/Stonehorn Dignitary;
Harmless Offering/Demonic Pact;