I think MK64 had the best fake items, though. They actually resembled real ones a little more and could deflect hits. I guess later on they worked as a junky item for people in first to get which wouldn't protect them from shells and the like, but that role was taken by the coin in MK8. I hate seeing anything be taken out of the game, with the exception of the thunder cloud (no offense, S07
). I don't think anybody liked that item.
As far as double item boxes go, I think those were in Double Dash only because of the two-to-a-kart mechanic. Each player could only hold one item at a time, though; in most MK games, you can hold an item behind you and collect a second in reserve.
The more I play MK over the years, though, I find that mushrooms are my favorite item in the game. When used right, they can be difference makers. In MKWii and MK7, they can even be used to dodge the dreaded blue shell.