Create a copy of a random card held in hand at end of round
Honestly, I think this works pretty well as a common deckfixing Joker. You're incentivized to play 5-card hands so that you're more likely to copy the card you want. (Although maybe it just encourages 5-card High Card? Not sure.) It might be somewhat hard to use at first, but it gets easier to use the more you deckfix. It's also kind of interesting since it actually works better with a lower hand size. What do you think?