You can add/remove rounds with wacky rules to your liking.
Related to this, a few games go really wacky with the rules while still not falling to the "completely chaotic" category.
Friese's (the guy who designed Power Grid, and a bunch of bad board games) Stich-Meister has separate rules deck and cards from that deck also dealt for the players. Before every hand all players simultaneously play one of their rules, and these rules specify various things for that hand, such as the trump(s) and scoring (plus or minus points for various categories), but also a bit more weird things like "the 2nd largest card wins", "the winner of the trick gives the cards to the player on the left", or "before the hand, everyone passes three cards to the right" etc. It naturally becomes very chaotic, but there's still strategy.
Ebbes specifies trump and scoring (which suits are positive/negative points) in the middle of the hand, based on the order cards of a certain number are played during the hand.
I also had a third game in mind when starting to write this, but I already forgot what it was.