Lately, I've been thinking more and more about cursers that give options. Some ideas:
$4
Debt Collector
Each other player may choose: Gain a curse; or the person who played this gains a Silver, putting it in hand.
Action-Attack
A card where you are stuck between slowing yourself down, and speeding your opponent up. If they dont take the curse it's a terminal silver, and once the curses are gone, it's completely useless.
$5
Poisoned Chalice
+2$
Each other player may choose: Gain a curse; or gain two Coppers, putting one on top of their deck and the other in hand.
Action-Attack
This one gives an interesting choice. You can get +1$ for this turn, but add two junk cards to your deck, one of which you will see instantly, or gain the curse.
3$
Salted Field
2VP
+2 buys
You may gain a curse. If you do, +1$
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At the end of the game, if there are no curses left in the supply, each curse is worth 1 VP instead of -1 VP
Action-Victory
This gives a second pile of estates that can run extremely quickly, but aren't worth anything unless they are all gone. Too weak? Perhaps, but I like the concept below the line.