Pillage/Counterfeit
You are gonna lose those spoils anyways, so why not double them?
Plus the spoils return before they can be trashed.
I actually find Pillage to be one of the worst Spoils targets for Counterfeits. If you play the combo every turn, you generate a whopping $4 using up an action, a buy and four draw slots. That is literally less than could get from just carrying 3 coppers and trashing/replacing 1 each turn. You could get a second Cfeit and then try to stack 5 draw into your engine, but that comes at the explicit cost of forgoing a Pillage buy/play.
Now Pillage comes with an attack that is very nice, but that attack makes it exceedingly unreliable to line up Cfeit with Spoils. First if I hit your Pillage, you may have no Spoils in deck for the shuffle afterwards. Second I can also disrupt the combo by hitting your Cfeit and forcing you to play your Spoils once. Regardless, Pillage is strongest against engines that have few clutch components where discards hurt the most (e.g. Golem, Kc); Cfeit, in contrast, thins and tends to help you buy double components (e.g. village & Smithy) where you will have a lot of redundant turns.
Bandit camp, for instance, needs only a net of 2 cards of draw to double play Spoils. That is a far stronger combo with Cfeit. Frankly, I would generally prefer something like Capital/Cfeit over Pillage/Cfeit for payload (the former generates $7 and +2 buys on net). Even with Marauder, you still have a nice shot for thinning your deck down for an engine, and eventually the ability to generate $7 in perpetuity at the price of 1 action and 3 draw slots.
Cfeit is, in general, a very good card and Pillage is situational but not too bad. It is nice to get them and line things up, but it seems like a very poor target as primary payload for an engine and not terrible reliable in a slog (particularly if you can do something else that is less finicky about lining things up, maybe like Horse traders/Duke or B-crat/alt-green).
It might be something nice to get, but I suspect than half of boards there will be a stronger combo there.