Vic Davis (a.k.a. Cryptic Comet) is responsible for a couple of quite nice games: Armageddon Empires and Solium Infernum. He has a new game on the way sometime - Six Gun Saga - but apparently it's taking longer than expected to finish (I know the feeling).
These games have a very distinctive common style. Each takes an very iconic setting - post-apocalyptic wasteland, Hell, the wild west - and makes it feel quite fresh. They borrow mechanics heavily from board games, with explicit simulations of cards, dice, etc., but take advantage of the computer's capacity to handle an amount of complexity and hidden information that would be unreasonable in an actual board game. But what I want to discuss here is something a bit more obscure: they take actions that seem like a mere formality and turn them into strategic decisions by attaching a resource cost.
In Armageddon Empires, you train and recruit various army units - mutant dinosaur riders, deranged cultists, giant robot tanks - and send them out to fight for you. But before you can send them out, you have to assign them to a group! You only have a limited number of action points per turn; creating groups and moving units between them uses these up, as well as the usual stuff like ordering groups around on the battlefield and building stuff. It's sometimes frustrating - I've trained up this Lovecraftian horror but I can't send it out to devour my enemies yet because I don't have a group to assign them to; I can create a new group for it but then I don't have the actions left to send it out. But it's not unrealistic - managing an army in real life has a lot of administrative overhead, and this simulates that somewhat - and once you get used to taking it into account, it becomes a small but meaningful strategic consideration. I have some actions spare this turn - do I move my scouting party to explore a different hex, or do I create a new group ready for the units I'll be building in a few turns time?
In Solium Infernum, the resource system involves drawing randomly generated resource cards, containing elements like "ichor" and "darkness", which you then use to spend on armies/relics/etc.. The cards generally contain more than one unit of these resources, and may even contain different types, so sometimes you're forced to overpay - e.g. if you want to buy something that costs 3 hellfire, and you only have cards with 2 hellfire each, you're going to actually have to pay 4 for it. They don't give change in Hell. It makes for a really deep and interesting system, because the 'actual cost' of anything can vary from turn to turn depending on how your resources are divided up.
Overpaying isn't always a problem - most items in the game are purchased through a blind auction system, so often it's desirable to pay more than the minimum bid anyway in order to overbid your competitors.
Where this system gets fiddly - and some would say unnecessarily so - is the constraint that you can only pay with up to six resource cards. This can be frustrating: numerically I have enough resources to pay for an upgrade, but they're spread across too many cards so I can't use them. It adds an extra axis of complexity to the resources - sometimes you'd like them in smaller chunks so that you're not overpaying, but other times you want them in larger chunks so you can actually use them to pay for the bigger items. You can spend an action to combine resource cards together, but actions are very precious in this game - initially you only get 2 actions a turn, but you can increase this to a maximum of 6 at great expense. So you're forced to make choices between preparing to buy something big or taking something small - basically it sort of means expensive items cost disproportionately more because they cost an extra action as well. There's a risk to this too - if you're preparing to buy an item at auction which then someone else purchases first, you might end up with resources combined in an undesirable way. And either way, there's at least one turn where you have this big combined resource card in your vaults, where there's a risk of another player stealing it..
You can also cast magic spells on your opponents, which costs resources. At the start of the game, you are asked to rank all other players in order of who you consider the greatest threat, and it will cost less to cast spells on opponents lower on this list. You can change this ordering at a later point, but that costs resources as well, so you have to weigh whether you expect to save enough resources from the cheaper spells for it to be worth the cost of changing it.
I've seen a lot of complaints about all these mechanics I've mentioned, and fairly so - they are somewhat fiddly. But they end up generating interesting decisions, which is kind of the point of strategy games, right? This seems to be a key element of Vic's design style: to take away something that players might expect to get for free, and make them pay for it instead.
(Another example of this kind of thing I can think of: in Red Alert, you didn't get a minimap display until you'd constructed a Radar building, and then you'd lose it again if your opponent destroyed that building or cut off power to it. Brilliant.)