Some responses:
"At most 2$ less" confuses me. I'd argue i can gain a card costing 0$ less, as it's "at most 2$" less.
Then you'd make the same argument about Saboteur, I suppose, since that's where I got the phrasing from (for consistency): "He trashes that card and may gain a card
costing at most $2 less than it." I think it's clear what both cards mean.
There are essentially no cards that would allow you to trigger this on purpose. Crossroads with no VP, or a bunch of various attacks, but really not much.
There are lots of reasons you would reveal cards: Crossroads and Menagerie always reveal your hand, anyway how could you even play a Crossroads both with a Hidden Passage and also no Victory cards? Diggers (Rebuild, Scrying Pool, Golem, Loan, Venture, &c.) and filterers (Wandering Minstrel, Scout, Ironmonger, &c.) usually reveal cards for accountability, Wishing Well/Mystic too for obvious reasons, and you mentioned attacks (Cutpurse is the obvious one, Pillage is similar, but Rabble/Fortune Teller/Oracle/Spy/Scrying Pool again, Saboteur/Knights/Rogue/Pirate Ship/Thief/Noble Brigand, all cause you to reveal cards). There are more that don't fit into those categories - Harvest and Tribute, for example.
Tunnel occasionally has the problem that there's no discarding on the board, but it still matters because it's $3 for 2VP, that's easy to hit in the endgame and more cost effective than Duchy if you have the buys, and alt VP being available at all makes engines more viable. I think gaining a Gold when you discard it is better than drawing a card when you reveal it, but not strictly better.
And the Quagmire idea I've seen many times before, although this one seems a bit more plausible. I might put it at $5 to make it more accessible, since after all you'll have to buy and trash both Duchy and Quagmire at minimum to make this worth it. Would actually be better with Shelters too, which is nice for an atl-VP card.
In a typical game you will trash Estate and Duchy, and then it's $6 for 4VP, again better value than Duchy. Of course you have to buy and trash a Duchy, but you do that
after getting as many as you can, so that you don't give your opponent a free ride. That means there could be a race for them while they are still worth only 2VP, because if you let your opponent piledrive them, they can make 56VP+. But if they split evenly or even 5/3, there's not much incentive to then trash a Duchy, so it's a Prisoners' Dilemma.
It's also intended as a counter to Rebuild, because let's face it, there aren't enough of those. At $5 I think it would actually help the Rebuild player more.
buy meteorite. Play it, taking the whole copper pile. Go duchy-duke.
This sort of thing is potentially a strong strategy with a clear first-player advantage, which is what makes this is one of the sillier cards. Gardens is a far better candidate, though - you won't be hitting $5 much after your next reshuffle. Either way it depends a lot on just how many Coppers you're playing with.
It's meant to fulfill either the role of Instant Chapel (play in the opening, take only enough Coppers to build up your deck), or Instant Three-Pile (end the game by taking ALL THE COPPERS). For both purposes it's important to note that it trashes your deck and discard pile, but not your hand; you can't trash away to a deck any smaller than what you drew with the Meteorite (and the Meteorite sticks around as a junk card, making Golem the worst card on the board), and conversely if you draw all your VP cards into your hand (Scout combo! I think that was the joke when I thought it up), they are safe.
But you are right, there are situations in which you do want to take all the Coppers at the beginning of the game. It is a silly card, after all (-: but I think in most games, it would not be particularly ridiculous.
