Variants by David Kuznick (david@ci.com).
To overcome the unbalancing nature of the Four Leaf Clover card, we (Alan Moon, Mike Schloth and myself) play that you have to roll two straights to win. I know others who play that you have to do two full rolls to win.
We also play with another rule that helps to elevate the game above Cosmic Wimpout. When you roll, you don't have to remove ALL scoring dice and set them aside, just at least one valid scoring combo (i.e. a 1, a 5, or a triple). This make for more interesting decisions; "do I take out those two 1's, or do I only take out one in the hopes of giving me better odds of rolling a triple?"
Finally, when you get a firworks card, if you get a full-roll, you turn over another card to keep rolling (and it's "safe". That is, if you flip a "turn over" card, you still keep your score). I don't think this particular rule adds or subtracts anything from the game, though.