So I thought of some cards and decided to post them here.
Upgraded Cellar - 3$ - Action-Reserve
+1 action
Put this on your tavern mat.
---------------
At beginning of your turn, you may call this. If you do, you may discard X cards. Then, draw X cards.
I think this is a nice little card, like Guide, which you keep on your tavern mat until you find use for it. The good part is, it let's you choose how much cards you want to discard and this is the point where I thought this should cost 4$, but unlike Guide, this has antisynergy with discarding attacks, where you'd rather have Guide.
Noble Fighter - 3$ - Action-Attack
+1 card
+1 action
Each other players discards down to 3 cards in hand. Each player who did, draws a card.
This might worsen your opponents turn, but if they have two cards they'd want to discard, this is a chance for them to have a better hand. They still have lowered handsize by one card.
Safe - 4$ - Victory-Reaction
1VP
When another players plays an attack card, you may reveal this. If you do, set this aside, gain Gold and Copper, then return this to your deck at the end of the game.
I thought of tunnel when creating this.
Golden Hoard - 9$ - Victory
Worth 1VP for each Gold in your deck.
This is priced very high, because golds improve your deck. If you get a lot of them, you can buy this for more points than a province. I am sometimes thinking of making it worth 1VP for 2 golds.
Small Venture - 7$ - Treasure
3$
+buy
Reveal the top card of your deck, if it's a treasure, play it.
A gold that chains with itself.
Sage's Scrying Pool - 5$ - Action
Each player (including you) reveals the top card of his deck and either discards it or puts it back, your choice. Then reveal cards from the top of your deck until you reveal one that costs 5$ or more. Put all of your revealed cards into your hand.
Should +action be present here? +1$ cost so you can't open with it on 5/2?
Road Builders - 6$ - Action-Reserve
Put this on your tavern mat.
---------------------------
When you call this, name a card. That card costs 1$ less until this leaves from play.
A delayed bridge, but for one card only. Gives you megaturn option, but you still require +1buys.
Craftsman - 4$ - Action
+Action
Take a coin token.
You may spend any of your coin tokens. If you do, gain a card having cost equal to number of coins spent.
A little card which you can use to stockpile tokens and then use them to gain a good card, or just support your current or next hand with coin tokens.
Innkeeper - 4$ - Action-Duration
Name a card.
Until your next turn, when any player plays the named card, take a coin token.
Playing against engines that focus on playing one card, like Hunting Party? Just play few of these and name Hunting Party.
Tithe - 2$ - Event
Each other player checks the top of his deck. If there's....
-card token, he takes his -1 coin token.
no -card token, he places it there.
Generally weak to buy, but can be good if you can buy it two times.
Burning Witches - 5$ - Event
Each other player trashes a Witch(-card) from his hand.
If they did, they gain 2 Golds, 2 Silvers and 5 Coppers, and they may trash a curse from their hand.
If they didn't, they gain 2 Curses.
You may trash a Witch(-card) from your hand, if you do, gain two silvers.
(If there's no Witch on the board, one random kingdom card is a Witch-card[it works like Bane card])
A trashing attack in an event. Thought it might be a good idea.
Craftsman V2 - 4$ - Action
+Action
Take a coin token.
You may play your treasures and use any of your coin tokens. If you do, you may buy a card, which you put into your hand.