One of the more unique approaches comes from Professional Sports Authenticator (PSA), which has assembled a team based around the players with the most PSA graded trading cards so far this year
The Defiance Band does exactly that, making attacks from the Pokemon it is attached to do 30 more damage as long as you have more Prize Cards left than your opponent
Lets have a look at another legendary creature from last year that has a similar, but even better ability in my opinion, Rashmi, Eternities Crafter
If this card in its owner's Spell & Trap Zone is destroyed by an opponent's card effect: You can add 1 "Harpie's Feather Duster" from your Deck or GY to your hand
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The deck wizard could provide more options for my taste, particularly with trainer cards, but it provides a good starting point for those who want to build a deck around a couple of cards, and to then iterate from that