First up is one of my favorite foil cards that I own: Rishadan Port from the Mercadian Masques set. I have this single foil copy and three regular copies and not one of them has ever been put into a deck and played with. It's been a Legacy format staple for a long time and I read it's been in decks that I wouldn't have even thought to place it in, like Goblins. Other decks that utilize it are Death & Taxes and Lands.
Now, mind you, I'm just throwing out these decks I've seen listed, but know very little about. I play mostly casual, and while I've watched a fair amount of Legacy and Modern tournaments online, I'm not the best with identifying which decks are which (except maybe Affinity, Elves, and Burn). Either way, because of its demand (many decks utilizing them use four of them) and low supply, the price of regulars have generally hovered around $100, while the foil has fluxed around $500 or so. Given I've never used them, nor play the decks wanting them, I'll just keep them locked up safe, especially my precious foil!
I'm pretty positive I'll never be able to collect the rest of my foil playset, even with the new foil Judge promos on the market for $200, so that's a bummer...
Repercussion (Urza's Destiny), on the other hand, was a card I played with a lot! Not this playset of foils (purchased for the infamous all-foil Burn deck), but my regular copies. I mentioned not playing with many creatures and this was a way to combat creature heavy decks when playing Burn. One downside to my Burn decks was that you could end up wasting too many cards targeting creatures, attempting to survive, rather than on players to win. Repercussion allowed those damage dealing cards being cast on creatures to be much, much more useful. Plus they stacked, so the more of the enchantment you had in play the more damage the creature's controller would receive.
I'd always have to be careful once placing one of these out on the Battlefield, and play a highly political game if multiplayer, because this essentially made me a huge target. It also stopped opponents with creatures from attacking one another too, as they would take damage from doing so.
Thankfully I usually had Ensnaring Bridges and/or a handful of cards like Cave-In or Pyroclasm, which deal damage to all creatures in play, so I could not only potentially clear the board, but deal massive amounts of damage to my opponents!
Repercussion is cheap, the foil being only $10 maybe, and I already own my playset. I've been hopeful that the card would be reprinted so it could have Modern format application, but so far no such luck.
Have you ever played with Rishadan Port? If so, which decks did you use it in? Do you feel that its current price is justified? Have you ever played with Repercussion? If so, which decks did you use it in? Do you think Repercussion would have applications in the Modern format if being reprinted?