This is an idea for a fan expansion I've been thinking about for a while. The basic themes are "a sudden, big effect" and things that happen when you shuffle. Some of the cards also have a Wild West theme.
It has some new mechanics.
First, it has the
Luck Tokens I invented for the weekly card contest. I had actually come up with these tokens when I was thinking more about this set than the contest, and they serendipitously worked as an entry. For those who didn't read the thread, "+X Luck" means you gain X Luck tokens, and you spend Luck tokens when you shuffle. For each Luck token spent, set aside a card and then put it on the bottom of the deck after shuffling (in any order if you set aside more than one).
There are some cards with overpay as well.
The most important, though, is the new
Jackpot card type, indicated with a bright green color. If a card has the Jackpot type, that means it has a special ability, indicated with the text "Jackpot: ". When you play a card as a Jackpot, you do not get the card's normal effect, and get the Jackpot effect instead. There is basically one important restriction with Jackpots:
You can only play one per turn. Once you play a card as a Jackpot, you can play other Jackpot
cards, but you can only use their regular abilities. When can you use a Jackpot?
Anytime on your turn except during cleanup. You can use it at the very beginning of your turn, before you resolve any lingering durations, or you can use it at the very end of your Night phase, or anytime in between. It does not use up any actions, the only restriction is once per turn. Also, these rules only apply if you're playing a Jackpot card
as a Jackpot. If the card's other type is Action and you play it as an Action instead, the normal Action card rules apply instead.
So here are the cards (more coming.) I'm pretty clueless as to whether or not these are balanced, so any feedback is greatly appreciated!
(10/29)

A great example for how you can use (or abuse) the Jackpot mechanic. Play a Cultist and immediately trash it for +3 cards, or get a Monastery effect by playing it after your Coppers. Use the top decking to replay the same card, or set up your next turn. Lots of possibilities. By the way, I came up with the top decking thing before Eagles posted about his similar Heir card. This has the same tracking problems, but I might find some way around that.

Note that the Jackpot says "card", not "Action card". Since you can play Jackpots at any time, there's no need to limit the King's Court effect to Action cards; you can use it on Treasures or even Night cards!

A cute idea I came up with. It's like Council Room or Governor, but then you can force them back down to 3 cards. The attack is also the Jackpot, so you can use it after playing another with the Action effect even if there's no +Actions on the board. The net result is only +2 cards, of course, but hey, you also got +Buy and attacked everyone else.

It's an attack village! You can potentially force them to discard anything thanks to the play-anytime Jackpot rule, but the village effect itself is pretty crummy, so you decide if it's worth it.

Card from the contest, with a minor change. Similar to Ducat, but I like the idea of a slightly-better card you can replace your Coppers with, to maybe make Remodeling easier.

Another contest card. Curses everyone, but at least they can make the Curse miss a shuffle. Originally it was going to be "+$2, +1 Buy" with the name being a nod to Woodcutter, but I felt, hey, if this is a witch that hands out Luck for some reason, why isn't she giving you any of it?

The last contest card, again with a minor change. You can use the Luck to make this dead card miss some shuffles, or just trash it and use the Luck to bottom-deck the Gold.

A card from another contest. This was an idea I came up with a long time ago, but it has overpay so it fits here just fine.

Yup, it's a $2 attack! It's also something that cares about shuffling. Instead of giving you Luck tokens, though, it gives everyone else bad luck. It has to be weak given the price, but is it too weak to ever buy? Dunno.
(10/31)

And here's the Treasure-Jackpot I promised. Directly inspired by Leprechaun, one of my favorite cards, but Treasures and Nights will also count toward the 7 here.

More crazy colors! The Jackpot is a bit convoluted, but I wanted something that you wouldn't obviously want to do at the beginning or end of your turn, so it has the Lab-Discard-Wharf thing.

A lab variant with a nod to Secret Chamber. It's not a Reaction but it could be a reasonable defense to discard and junking attacks.

Another wacky effect. Empty your hand of all Treasures and Nights, then return to your Action phase and draw back up to 5.

It's the infamous Road! But you can't play it infinite times, at least. Note that while it can
use your turn's Jackpot, the card itself does not have the Jackpot type, so you can only play it during your Action or Buy phases. If it's not clear, you get the $2 and nothing else if you play it during your Buy phase, and you get everything under the $2 but not the $2 itself otherwise. And you can't use any Jackpots if you do the return-to-hand thing. I made it an Action-Treasure so that the return-to-hand is still useful even if there's no villages.

Same principle as the last one.

More boring than the others? Eh, it's a village and it helps your engine consistency; it works.

Another old idea. Sift, or "reverse-sift" before trashing your hand.
(11/15)

Edict mechanic from Asper. I wasn't planning on having any landscape cards originally, but then this silly idea came up, and I think having some when-you-shuffle Edicts could be cool. This was originally going in RBCI, but the more I thought about it, it might actually be fun to have a deck where your Treasure is constantly multiplying. Might lead to some nice TfB tricks, or a combo with a good Kingdom Treasure. What do you think?

Another overpay card. The on-play is weak, but getting rid of some of those $0 cards can get easier if you use the overpay to replace them with 2s. And of course, you can also use the overpay to get some extra points or empty a pile at the end. It's like VP for overpay but not broken.
(11/19)
New card, with a new color combination!

The basic ability is pretty bad: Copper as an Action. The Jackpot ability gets a bit more exciting: you can get a Village effect, or return to your Action phase if you draw it dead. And then there's the Reaction part, of course: Stop Attacks cold, at the cost of next turn's Jackpot. Which will you choose?