How about a selection of booze you can only buy at taverns that actually get you drunk.
Screen blurs, weird sound (both worsening the more you drink) and you look and move around like a drunk.
It's all just for immersion and depth and completely down to the player to participate or not. It's just a bit of fun and ofcourse once you buy a few, you can equip and use em anywhere.
What you all reckon?