My original design was: You may choose to not untap CARDNAME during your untap step
But this isn't Top Ten Cards on the Commander Ban List That Could Be Pulled Off
Before you can decide what cards should go in your Magic: The Gathering deck, you need to know how many you need to include
Donating Bulk Cards If a player's collection is huge, and those cards are gathering dust, then it may be time to pass them on to a new owner
Zone Replacements A lot of replacement effects are about sending a card to one game zone (exile is the most common) rather than where they would normally have ended (usually the graveyard)
Not normally, but if Shellephant has first strike, double strike, or triple strike, and the creatures it's in combat with have none of them, you can deal damage as a 3/3 and then change it to a 1/4 before normal damage happens