Swap Card

The Swap Card is one of the items used in Mario Party 4 and Mario Party: The Top 100. It allows the user to swap items with an opponent randomly chosen. This is the replacement for the Barter Box, although the latter lets players choose who they would exchange items with and is much rarer than the Swap Card.

Official description from Mario Party: The Top 100
Swap Card:

Dump all of your ho-hum items on a rival in exchange for all their sweet gear.