Impact of time of day, moon phase and other celestial events on gameplay (magic strength, teleporter targets, siege events, quest steps, NPC schedules etc)
massive number of animated emotes that can be learned from NPC or other player
sit on chairs, eat and drink, sleep on beds, lay in bathtubes, douse yourself with a bucket of water ...
dialogues with NPC based on keywords and response
extensive music system for im promptu plays solo or in band as well as prepared concerts, pre-recorded music, radio - and even real-world artist album releases parties
ingame messages on digital paper or player written books with formatting options