I suppose I'll make some suggestions as well since players who want to discover combos for themselves can just opt to not read new posts in the thread.
Procession/Fortress is a strong combo if there are power 5s in the kingdom, especially terminal draw. Procession-Fortress gives you +2 cards, +4 actions, lets you gain a $5 card, and the Fortress returns to your hand. With terminal draw, you can end up playing several Processions on the same Fortress in a single turn.
Procession is also a somewhat amusingly effective trasher for Ruins, since you get to play them twice and trash them
But unless it's worth trashing those Ruins, it's probably not a good idea to get a Procession just to trash one...
In general,
Procession works decently with Attack cards that end up losing their ammunition (Cursers and Looters), though I guess matching them up in a junked deck is kind of a crapshoot? Still,
Procession-Marauder gives you a $5 card and 2 Spoils, and
Procession-Cultist yields a juicy +7 cards. I have a hunch that it's good in conjunction with cheap card gainers (such as Ironworks) given the presence of halfway decent kingdom cards at $3 and $4 because it gains $5 cards, gets the $4 card out of your deck, and also plays the $4 card twice for a nice benefit. I actually think that it's much more adequate to view this card as a
trash for benefit card instead of a Throne Room variant.
In a similar vein,
Develop/Fortress may be a somewhat legitimate combo, but you really do want a terminal drawing $5 in the kingdom, or maybe a good non-terminal $5 and a terminal drawing $3, otherwise you just end up spinning your wheels. Fortress returns to your hand and can pick up one of your newly topdecked cards.
I tried a game today with
Rebuild/Feodum and it absolutely dominated, although I am very slightly skeptical as to its actual effectiveness, because that was a 3-player game where I ended up gaining 11 of the Feodums in some fashion and trashed 5 of them for 15 Silvers. The goal is to Rebuild starting Victory cards to Feodum and Rebuild Feodums to Feodums until the pile is out. Once Feodums are out, name Feodum on Rebuild plays and trash Duchies to Provinces.
So my personal opinion on Feodum is that it really wants to trash itself, because it's otherwise difficult for it to become a high-scoring card; obviously the problem is that you'll have fewer Feodums to score with. (And also obviously, you'd ideally want to have # of Feodums and # of Silvers / 3 as close as possible). In a 2-player game, assuming that one player is uncontested on the Feodums, he's only going to have maybe 4 Feodums scoring ~5 points each? The good thing is that denying Feodums is a rather weak move because most decks won't even have 6 Silver by the end of the game.
I'm hypothesizing that Feodum is really not a viable alt VP strategy in and of itself: the Feodum player must go for Duchies and steal Provinces as well. Except for a very long, drawn-out game, I don't think that Silver-gainers in and of themselves are adequate support for a pure Feodum alt-VP strategy (assuming Duchy buys, of course). Perhaps something like Hermit/Feodum is stronger than Workshop/Feodum or Ironworks/Feodum by comparison.
Rebuild/Tunnel is a neat combo, but probably wants some sort of handsize increasing card or sifter as well. Rebuild starting VP to Tunnels and name Tunnel when playing Rebuild to gain Golds.
Trader/Feodum is pretty self-explanatory...
I'm hesitantly going to suggest
Counterfeit/Marauder, but I don't suspect that it's particularly effective. Marauder will junk up decks (making Provinces hard to buy) and hand out Spoils; Counterfeit-Spoils automatically nets $7 and doesn't present any drawback that playing Spoils will normally incur. Getting the Counterfeit is probably difficult in the first place with a 4/3 Marauder opening, though. On the other hand,
Bandit Camp/Marauder gets you those Spoils and doesn't encourage a junked up game. You can actually probably build an engine that relies on consistently hitting Counterfeit-Spoils for a huge amount of coin.
I suppose in a similar vein,
Counterfeit/Market Square is a weaker variation of that combo: Market Square reacts on Counterfeit's trash to gain Gold, and Counterfeit double-plays Gold. You'll want an engine to do this one, though. For engine decks, Counterfeit/(Spoils/Gold) is a quick way to get a lot of coin when you need to, for example, be reaching $16 for double-Province turns.
Wandering Minstrel is a nombo with Looters. Wandering Minstrel may be actively bad for your deck in these games because they discard Treasures and leave Ruins on top.
These are combos that I haven't tried out but may work in theory:
Scavenger/Stash is something that we didn't play with, but Turambar and I talked about it and it seems super-strong. Get 2 Scavengers and 3 Stashes and you can Province every turn regardless of cursing, looting, trashing, or deck-mucking attacks. Honestly, probably way better than Chancellor/Stash, which was good already. The only failure mode is if your 2nd Scavenger ends up being the 5th card of your deck, which has a miniscule probability of happening.
Beggar/Gardens looks like it can be amazing. Beggar gives +$3 and gains 3 cards that maintain the desired average quality of the deck. Probably hugely dominant with some +buy to get multiple Beggars to start out.
Beggar/Duke, on the other hand... Looks good on paper because Beggar gives +$3, but honestly, Duke rushes want something better than tons of Copper. I don't think Beggar will be a particularly good duke enabler.
Apparently
Death Cart/Rats may be good; I feel like straight Death Cart isn't that much weaker, though... Probably an easy way to get coin and slim down a deck for an engine?
Storeroom/Tunnel looks to me like a power combo when it appears. It has huge discarding reach (discard aggressively and you go through 8 cards per turn, including the 4 that start out in your hand), it sifts on the first discard, it discards Tunnels for +$1,
and it gives +buy for when you have a lot of Golds. Might be improved significantly with non-terminal draw.
Hamlet/Poor House looks like it could be hilariously strong. Will probably really like some kind of draw.
Looters are probably a nombo with Scrying Pool. Seriously, Ruins won't hurt SP at all, almost. It just decreases the chance of starting the turn with SP in hand, but the guy will draw all of the Ruins anyway.
