I really enjoy both alt-VP and trashing strategies, to the point that I will bend over backwards trying to make that kind of strategy work, even if there are other, clearly more favourable options.
So obviously my favourite card is Bishop. It does both! The first time I bought a Peddler for $0 and then trashed it for 5VP, ah, that was sweet nectar. Mmmm....
Also, if there's even a remote chance to make Tunnel work, I will grab Tunnels. After all, the longer the odds to make it pay out, the more satisfying when it does... or if there's a way to cash them a preposterous number of times (i.e. Golem with only one unspent Action card), that's fun too. There was a game where the only discarding option was Farming Village, so of course I had to open Tunnel/Farming Village. It worked on the third run through the deck... so happy! :-)