There's a billion and a half RPG systems out there. And...let's face it, a lot of the big popular systems are the equivalent of AAA computer games. They have easy-to-grasp systems, and aren't too hard to get into. Often their systems are cool and unusual, but they're still well-enough known that you can find a book at any local hobby shop.
This isn't about them.
Let me start off with one of my favorite systems, even though I've only played one campaign of it. Deadlands. It takes place in the "Weird West", kind of an alternate-history Wild West where everything went to hell. Like...really went to hell. THAT hell. It's about 2/3rds of the way to Call of Cthulhu, except with a very different setting and totally unique game mechanics. If you liked the mood and "oh god we are outmatched" feeling of Call of Cthulhu, but wanted to actually win against your enemies on a semiregular basis, you might like Deadlands.
First, let me start off on the dice system. It's pretty cool, I like it. You have the usual assortment of stats (things like strength, agility, etc). And (simplified), your stats are rated by die type. So a seriously weak guy has d4s in strength, while a maximally non-supernaturally-strong guy has d12s. You also have points in skills that are tied to attributes. These are the numbers of dice you roll. Three dots in Rifle, and d8s in Deftness? You roll 3d8 to shoot. You only take the highest die...but if you roll the maximum value (IE, an 8), you roll again and add to that die. You also get a limited number of Fate Chips per session, which you can spend for extra dice, or to add another die to your highest value...or you can save them to cancel out damage, or to get extra experience at the end of the session. Feel like taking your chances?
Being wounded really sucks, as you might expect. Each limb gets five wound points, and an only-slightly-elaborate system transfers weapon damage into wounds. Your highest wound anywhere on your body subtracts directly from most rolls. Yeah, life is not very good when that happens, especially when you're only rolling D6es. Don't get hurt. This isn't D&D.
...But enough about the mechanics. The West is weird for a reason! There's demons out and about, and they really, really want to bring fear to the world. Fortunately, you can actually have some amount of super powers. Hoyle was a demonologist, and Hucksters who studied his works have learned to make deals with devils to cast spells, through essentially-instant games of poker; your skill determines how many cards you draw to make the best hand you can for damage or awesome effects, but don't fail to make anything or it's...bad. Mad Scientists (YES!) have a similar mechanic, but can create things over time, powered by the recently-discovered Ghost Rock (think 'all the power of uranium, but it burns like coal and is barely used up'). A fairly inexperienced mad scientist can get the inspiration to make gatling pistols or some sweet body armor, and no, they are impossible to assembly-line. A gifted Mad can make autocarriages, ultra-fast trains, jetpacks, sleep rays, or...well, just like the Huckster...how good of a hand can you draw? There's also priests who can channel the powers of God, and there are Native American powers... It sounds like it could get silly, but trust me, it's not. With a talented GM, this game is designed to be scary. as. fuck.
I like it. What do you like?