I was recently exposed to Spellcaster, or "Waving Hands," and was immediately excited to try it out. The logistics prevented me from trying it for a while, until I found a site that hosts automated sessions between players at RavenBlack Games (I'm Ellipsis on there, so if anyone wants to create an account and send me a challenge, feel free). Now that I've gotten to actually play the game (a dozen or so times) I can say that my excitement was justified.
Spellcaster is a game about dueling wizards. Nothing terribly innovative there, seeing as how an entire gaming medium (the collectible card game) was spawned by a game with the same premise. The innovative part is how you cast spells - by making gestures with your two hands (usually abbreviated as letters you can write down in sequence), combinations of which create spells. Now, this is conceptually very cool, but that's not what makes Spellcaster a good game. It's the fact that the gameplay is very simple (just consists of picking a gesture to make with each hand each turn), but very strategically deep. We can be a bit more specific, though, in talking about what makes the game good:
1) Micro-goals with feedback: Each individual spell is made up of several coordinated actions and could be counterspelled or otherwise interrupted by an opponent. As a result, every individual spell that you complete gives you a sense of accomplishment (proportional to the difficulty of completing the spell).
2) Engagement Level: The game allows you to control how much time you invest in it. There is no time limit between turns, so you can take as long as you want to make a decision. You can check on the progress of the game every once in a while (or just get an email reminder when it's your turn) and play at work. Alternatively, you can spend time strategizing, trying to figure out your opponent's plans, etc, and this time pays off. The ability of the player to control how they play can be very valuable.
3) Balance: Sure, the big spells are flashy and do a lot of damage, but one interruption from your opponent spoils the effort you put into preparing that spell. Meanwhile, the minor enchantments only affect your opponent for one turn, but they're easy to pull off and can disrupt his rhythm. What particularly pleases me about the balance is that even though there are different play styles, every spell is useful to every player - sometimes, a situation just calls for "remove enchantment" or for "anti-spell" and this is just as true for a defensive player as for a fan of the big, flashy spells.
4) Dynamic: You will never succeed at this game by picking a "dominant" strategy and going through the motions. The game relies very strongly on predicting what your opponent is going to do (so you can counter their attacks and make sure they're unable to defend themselves from yours), and the result is that play is very fluid and often unpredictable (your opponent is working very hard to make sure it's upredictable!).
5) Come Backs: The game does not provide any means for the winning player to secure and easily hold onto his lead. If one player has 5 monsters out and is invisible and immune to fire, cold, and physical attacks, all it takes it one dispel magic to level the playing field. Similarly, even if you hit your opponent with a strong spell, they might have something up their sleeve that they've been planning for a while that will take away your advantage. The point is that I've had many games where I was clearly ahead and ended up losing, and many in which I was clearly behind and still pulled out a victory.
This post, of course, isn't just an extended advertisement for the game - these basic elements that make the game compelling are elements that should be included in any game that strives to be strategic, because they are the elements that create a rich play experience. To balance out the post a bit, I can quickly point out the major problem with the game: steep learning curve. The only people who play this game are those who committed themselves to learning how to play it, and who are willing to repeatedly look over the 40+ entry spell-list trying to figure out what kind of options they and their opponents have, and what the advantages and disadvantages of each are. If a game had this kind of strategic depth and was able to lead players in and teach them the skills they needed in a more incremental way, it would be the stuff of greatness.