Seems like every game has its own system, or unique game mechanic. Share ideas on how to deal with some of the more difficult systems, or ask questions on the finer points of using a specific system or running a specific game. Also a good place to talk about newly discovered games or game systems.
I think to start, I'll just drop a couple of links to sites with free/open game systems, that people can use as alternatives to more costly commercial games, or as simple one-shot tryouts for pick-up games, when the GM and/or players aren't in the mood for their regular gaming.
1000 monkeys, 1000 typewriters (1km1kt): http://www.1km1kt.net/cat/rpg
Chris' Compendium of Free Roleplaying Games: http://www.homebrew.net/games/
The Free RPG Blog: http://www.thefreerpgblog.com/
John Kim's List of Free RPGs on the Web: http://www.darkshire.net/jhkim/rpg/freerpgs/
A blog I recently posted with advice on running games. I think this forum is appropriate.
Depending on what you're looking to run you can sometimes get tired of the more complicated game systems. 4e, while not that complicated, can wear on you with extended combat scenes. Shadowrun is a bear, D20 modern is a pain in the butt but it's fun. Sometimes a DM/GM wants to run something that requires less prep and rules and more role playing and fun. Some examples:
Complicated RPGs to try: Shadowrun, AD&D, D&D, D20 Modern, Teenage Mutant Ninja Turtles and other Strangeness, Rifts, GURPS
Simple RPGs to try: Grimm, Mouse Guard, Swords and Wizardry, Gamma World
Never had a problem with "complex" (or "crunchy") systems. I learned a great many tricks over the years to streamline gaming under any system, ranging from custom character sheets (as in, "custom for each character, containing only relevant material") to charts, booklets, custom screens, and a short deck of flash cards next to my right hand (printed on index cards) with each character's vital summary.
Don't get me wrong, simple systems are OK, but complex systems don't bother me or my group. The main thing is never letting the game system get in the way of the game. Our current group is in the midst of a Rifts campaign, and I've been told on more than one occasion on this site that Rifts is either very slow going or I must be an astounding GM to run it so smoothly. I believe it's just a matter of preparation beforehand, collecting and refining the GM aids over time. My longest campaign ever was a Rifts campaign, once a week for five years. Not once did anyone complain it was "too slow" or "too complicated".
I also believe that simple systems are good for some games, but a complex world tends toward a complex system. For example, Rifts with its magic AND high technology, as well as its multiple dimensions, tends to lend itself towards complexity. And the world is WAY too rich and detailed to pass up over a game system. It's not perfect, not by any means, but it works fine.
That's true, my group and I have never had a problem with complex systems and I own the hard copy of all of the major game systems. But for a group starting out that wants to just run and gun with a simple system sometimes it helps to identify what you can just run with and which you need game aides and custom sheets for.
I'm not putting down complex systems, Shadowrun is one of my favorite settings, just identifying which ones require less reading for those 'dice challenged' DM/GMs out there. But that is a good point, never let the rules get in the way of the game or the fun.
I know a lot of people are not a huge fan of rules light systems. I find these systems to be a great way to express creativity and to try out experiments in the area of enhancing a game. It allows you to find a balance between to much and not enough. I am not saying in a heavy system you can not do some creative adding of something just that it is easier to use a rules light system. For a game that uses imagination to express the game through that medium as a whole creativity would be that path you would follow and make new paths to discover a depth into a game. Tailor making a scenario or campaign for the players is great. Having some tailor made mechanics or enhances in areas of the system is even better it gives you that special presentation that only you offer thus making it unique and ensures that the players want more and will return.
One way to categorize rules is how easily they are applied to in-game situations. Consider an rpg where PCs have an attack score, and they add 1d6 to it and compare it against an NPC's defense score, and this is the basic combat mechanic. That's really simple and easy to understand, but what if the rpg doesn't say anything about attacking inanimate objects? What happens when the PCs wish to attack a rope that's two hundred feet away, or the hull of a starship, or a window?
The answer is obvious, right? The GM figures it out on the fly. Anybody can come up with some arbitrary "defense score" for these situations. However, what's basically happened is that the rules aren't doing any of the "heavy lifting" here, but have instead pawned it off onto the GM's shoulders.
I like rules, whether they are simple or complex, that give me actual values for resolving situations I'm liable to come across when I run whatever game the rules purport to be for. In the above example, if there was another rule that said "inanimate objects can be successfully attacked if the player rolls 2+ on the die," or "...if the player's combined score is 10 or better," or anything like that, then the rules have indeed addressed that situation. It may not be what I agree with, and it may not be balanced, but at least it's one less thing I have to think about when I run the game in question. When rules don't do that, I'm always left with the feeling that I might as well run my own setting and play rock-paper-scissors for the resolution mechanic. Some GMs, to be sure, are very happy with doing just that, but it's not me.
In one sense, this is a special case of considering rules that are complicated in-play and those that are complicated outside of play. Rules that seem deceptively simple outside of play, may lead to longer and more stressful play sessions through the sin of omission. To use a non-combat example, about a year and a half ago, I picked up a relatively new science fiction rpg that had a chapter devoted to an "adventure generator." I love these things, because they usually give me a new perspective on my own adventure design. However, going through the generator, it was nothing more than a series of NPC and item lists. For example, there was a "bad guy table" that you could roll on to get a result like "robot" or "alien." Not to put too fine a point on it, when I'm running a science fiction game, it usually occurs to me that the party could indeed encounter robots or aliens, and that some of them might in fact be the "bad guys." Basically, the adventure generator was a listing of random, generic elements, with no thought at all for what actually makes an adventure an adventure, that is, the plot, the situation, the obstacles, the lures, and how they might fit together and interact with the PCs. If I used this adventure generator on the fly, I would be totally stuck come play-time. It was a deceptively simple system that led to greater complications due to omission.
Another aspect of rules that don't often get addressed is the question of layout. I can handle complicated and complex rules if they're grouped in logical ways. By the same token, even if the system is very simple, if individual rules and exceptions are just scattered here and there I have to do one of four things. 1) I can ignore the rule, which is what I suspect happens quite often to these rules. 2) I can commit the rule to memory, which might happen if I otherwise love the system, but is generally a dicey proposition. 3) I can spend in-game time looking for the rule when it crops up...assuming I remember it even exists. 4) I can take the time during game preparation to record it and similar rules in my own notes...again assuming I remember the rule exists, and that I have a reasonable expectation that I might encounter a situation that uses the rules. Situation 1 means the game has wasted space: it took time to describe a rule that's never used. Situations 2-4 basically require effort and time that could have been avoided if the game had just been organized a little better.
On the other hand, if an rpg organizes its rules effectively, and I know what book and section to find the relevant rule simply based on the situation that develops in the game, that saves me time, makes my life easier, and makes it easier for me to tolerate complex rules.