I really like the way the Universalis game mechanic makes you spend coins for everything that you do in game. I was thinking about making a similar game mechanic in a game with individual Player Characters (you know, with their own stats and everything) but I really don't know where to start. Is there already a game with some sort of point-spending mechanic, where everything that is done uses some sort of, I don't know... currency-like system?

J.F., I don't know if it's exactly what you're looking for, but my own game, Unistat, has a currency exchange mechanic. Specifically, the resources are dice, and they shift and flow throughout the course of a game. There's a bit of uncertainty there that isn't present in Universalis, and you don't use your resources all the time...just when something important and disputed is happening. Unlike Universalis, it's a closed system, where all the resources in play at the start of the game are there at the end, but in different hands.

The game is pretty short, though, and free, so you can check it out and see if it's anything like what you are looking for. The direct download link is in my signature below.

Also, Nighttime Animals Save the World is the game I stole liberally from when designing Unistat. I can't seem to find it online at the moment, but it should be out there somewhere.

Universalis started life with traditional player characters and character creation inspired by Hero Wars/Quest.  It didn't work well.  The rules to make PCs work proved unnecessarily cumbersome and the game didn't really start to sing until I finally listened to Mike and scrapped them.  There are several variations on the web site that provided gimmicks for adding PCs to Universalis...to-date, I've yet to see a successful actual play report using them.

Is there something specific you're looking to accomplish with adding PCs to Uni like rules or is it more of a comfort / familiarity thing?

If you're just thinking of the very basic idea where the character has a resource that's spent to do something, I suggest looking at Noblis and the recent diceless Marvel superheroes game, both of which feature a sort of currency that is spent to engage in actions.

Oh, right. Of course, you can run Universalis itself using the PC rules gimmick. In fact, I've done just that, though I didn't write up any actual play for that game. We had a rocking Earthsea-meets-Conan game with noble thieves, brutal warlords, and evil sorceresses. The game jumped back and forth between different eras, and the world was torn apart and rebuilt, with the sins of the past troubling the hope of the future. Yeah, awesome.