I've been playing Winter Voices lately, and while it is broken in many ways, and you basically need the patience and forgiveness of a saint to be able to appreciate it, there is one thing about it which is pure brilliance: the skill `tree' (it's shaped like a snowflake). Not only is it and the artwork for the skills it contains very pretty: http://www.wintervoices.com/contents/screenshots/0/talents.jpg , it's also brilliantly build up. The straight lines out of the center contain the usable skills, and form skill paths (all skills on one line are thematically related). The skills in between give advantages to skills on both sides (it's a bit more complicated than that), creating a big interconnected network instead of isolated paths. It's a joy to traverse.

Anyway, to get to the point: are there any other games with skill trees as beautiful as this one, be it in shape, balance or artwork? For me it's basically the only thing that keeps me playing WV (though *some* of the battles are also very interesting and it's got a lot of atmosphere), so I figured that if something similar was embedded in a good, or even just decent game, I'd like it a lot.

I always love Final Fantasy X's Sphere Grid.

Oh wow, awesome. That thing is huge. (by the way, gamefaqs doesn't allow direct links, this one should work: http://www.gamefaqs.com/ps2/197344-final-fantasy-x/faqs/20045 )
This is exactly the sort of thing I'm talking about (too bad I don't own a ps2).

So do you buy the slots with XP? Or do you fill them with something else?

I can't think of a game that fits your topic but regarding artwork, Armegeddon Empires and Solium Infernum are two of my favourites. The card portraits in Empires are evocative and so full of character they really bring the game alive.

-edit- never mind misunderstood OP lol.

I'll just quote the Sphere Grid FAQ for the basic mechanic (and because I finished the game years ago, so I forget a lot of things): The crazy things you can do to Sphere Grid happen around halfway through the game (before that, the skill trees for each character are pretty much non-overlapping and linear), when you start to receive (a.k.a willing to grind) rarer spheres. You can use clear spheres to basically erase the whole skill tree and replace them with higher level attribute spheres (e.g. replace a Strength +1 sphere with a Strength +4 sphere), or use a teleport sphere to 'jump' to another character's skill tree on the other side of the grid, so the designated black mage can now learn white magics or become a thief, for example.

<grins> not on topic, but you did manage to bring up my other weakness: games which use ccg-like cards. aaaah.. beautiful. When traversing the skill system becomes a game itself, I'm very happy. Too bad this style of character progression isn't more popular.

I tried google image searching for `skill/talent tree/grid', but that returns mostly WoW trees. Not to say those aren't nice, very balanced and quite pretty, but also kind of boring and rigid. Pretty much the best execution of one of the least exciting kinds of skill trees.

And it became worse with 4.0/Cataclysm, now you're forced to chose only one of the three trees your class has until you spend at least 31 points in it (just enough to get the bottom/final talent). Earlier I could mix and match pretty much as I wanted (and not be great at anything, which suits me better than the current system). And after those 31 points are spent, you don't have much left for branching out even at max level.

Diablo 2 patch 1.10 or later has a fairly intresting talent tree mechanic. Its no where near as intricate as the 2 skills trees listed in this thread already, but it uses a synergy system. Different skills add bonuses to other skills in the tree. Its mostly damage increases rather then anything else but thought it was worth a mention.

I've been thinking/looking around a bit more, but the only thing I've come up with so far is the tech tree of sword of the stars: http://ouroborus.org/sots/map.html
Not really a skill tree, nor is it really beautiful (though in game it looks not like this at all), but it has the `using the tree is sort of like a game itself' thing: everything is interconnected, but not every path is guaranteed to be there (the numbers you see next to the paths indicate the chances of the path showing up for different races). Choosing to what to research next is much more a conscious decision dependent on the situation than with the usual tech trees, because you can never be entirely sure a path leads where you want it to, there is a certain risk involved. It would be interesting to see something like this in a RPG..

I would just like to say that I think the Witcher has fantastic looking skill tree too. :)