I keep my player's trust by trying not to be a prick. This often involves listening to them. I've found, on the whole, the rules themselves don't offer me much help in the 'not being a prick' department.
Yeah, I agree with not being a prick. I listen to my players. But there's only so much listening you can do before you just have to put your foot down for the good of the entire game.
And when I need to put my foot down, it is much easier for me to say "No, you can't have 500 hitpoints because the rules say so" than it is "No, you can't have 500 hitpoints because I don't think it'll be very much fun." I find my friends react better to the former than the latter. In the latter case, they are thinking "Of course it'll be fun, monsters won't be able to kill me. I'll be super tough!"
I find most players aren't very good at considering the impact of their actions on the rest of the group. In fact, with my players, they see each advantage they have over the rest of the group as part of the benefit they get for putting in the extra effort to come up with the idea.
In the really good RPG campaigns I've played in, most of the most-good stuff occurred in a place outside of the rules, in a magic land of ad-hoc rulings, fiat, negotiation between DM and players, and pure, unadulterated 'Aw Hell, that's sounds cool, go for it!'.
Trust between the people at the table makes this possible. Formal rule systems, and the agreement to follow them more-or-less to the letter... not so much. The best part of these games is going outside the rules, making a game out of unfettered --partially fettered?-- imagination. If i wanted to play a great game where everyone follows the rules, I'd being playing chess.
It can be, I'll give you that. Sometimes the coolness comes from that one time cool maneuver. However, I think it's because I've played SO many different RPGs so often that I've found that the things people come up with are often similar to each other.
Over the years, I've seen like 30 people all decide that something like "I make the roof fall on his head", "I grab his arms so he can't attack anymore", "I trip him using the carpet", "I push him into the pit", and similar things are extremely original ideas that should succeed in bypassing an entire encounter.
The thing is, people don't go outside the rules because it's cool, at least most of the time. They go outside of the rules to gain a benefit that the rules don't offer them. Most of the time the benefit (at least in combat) that they are looking for is an increase in damage up to and including instant defeat of the enemy.
And in these situations, you run into a problem(the same problem that occurs in most of the stock 3.5 edition rules): If a move is that much better than "just attacking" then you need to make it have a much lower chance of working or a reason you can't do it every time. Otherwise, it becomes the default move for everyone.
For example, if you have a move that can completely incapacitate an enemy, you've won. So, for that move to be balanced, it needs to have approximately the same chance of defeating an enemy as a normal attack does. So, if a normal attack has a 50% chance of hitting for an average of 10 damage and the enemy has 50 hitpoints, it takes on average 10 rounds to defeat the enemy.
You need to have approximately the same number of rounds to beat an enemy using the "I grab the enemy and pin him so he can't fight back"(or "I shoot the ceiling to have it fall on him and pin him to the ground" or whatever special idea someone comes with with to win immediately) special rule. Which means you need to have only a 10% chance of succeeding if you allow someone to use that as a maneuver. And even then, normal attacks have basically 0% chance of defeating the enemy before round 3(if they hit every time and roll maximum damage, they still only defeat the enemy once they have lowered him to 0 hitpoints). So, that still makes the theoretical "I win" rule more powerful. So, you have to lower it's chance to hit even further(especially if you are playing a game that might allow someone to increase the accuracy of the special maneuver). If you are using a d20, you can only lower it to 5%.
So, basically, you have to tell someone coming up with a special move "Alright, roll a d20, if you roll a natural 20, you win, otherwise nothing happens". In which case, no one takes the option. If you make it better than that, then anyone with a head for numbers tries it over and over again.