Vagabond, $5, Action-Attack
+$1
Each other player chooses one: he gains a Curse; or he reveals his hand and discards the highest costing card in coins in his hand.
i've playtested Vagabond and you guys are quite right, it's a $5. at $4 it felt too strong that everyone could buy it within the first 2 turns, and at $6 it felt too weak (we had Witch in the same game). at $5 it gets rid of useful starting Action cards or Gold a lot of the times but isn't as crippling as Torturer or Mountebank. that said, a few of these played in a row was super effective especially when the Curses ran out. having to reveal your hand before discarding is nasty too. interestingly, buying Provinces and Duchies seemed to be the perfect counter to Vagabond, and gaining that Curse mid game is often the better option. turned out to be a really fun card to play.
But after Curses run out, don't you just pick gain a Curse every time? (Like with Torturer.) Also, I'm a little surprised that this would be not totally outclassed by Witch at $5. (Although maybe it's because you assumed that you were forced to discard after curses ran out.) +2 cards is probably better than +$1, even in cursing games, and the optional curse-gaining is weaker than witch's mandatory curse-gaining; you can block it with province and maybe even duchy a lot of the time. If you're going to leave the wording as is, you may want to tweak the vanilla bonus and/or the price, so that it doesn't compare so unfavorably to witch. Then again, that's witch, and maybe it should be weaker. But with this and witch on the board, I think witch would almost always be preferred.
Otherwise, if you want to make the discarding forced after curses run out, you can say "Each other player may gain a Curse. If he doesn't, he reveals his hand and discards the highest costing card in it, in coin." But then I really think this needs a limit. Cutpurse is the only card (I think) which can force you down to a hand size of less than 3, and Pillage and Taxman, the two discarding attacks that can make you discard something "good", only go down to 4. I don't know how to define "good", but I feel like this should be classified as an attack that makes you discard something "good", and if it forces you to do that sometimes, then I think it needs to have a limit of 4. But then you run into the problem of players just choosing that option every time they have only 4 or fewer cards in hand, and then dodging both that and the cursing. I'm not really sure how to solve that problem, so I would just stick with the wording you have now (where the attack dies after curses are out), and play with the vanilla effect and price.