I've been thinking about trying to write some scenarios for existing games, and I figured that to help with that I should read some and, if possible, play through them. I started with Alone Against the Flames, a free solo downloadable adventure for Chaosium's Call of Cthulhu role-playing game (specifically, the new 7th edition). You don't need to own the game to play it; and in any case, the 7th edition quick-start rules are available for free download as well.
It was a fun way to spend an hour. My character (investigator in the game's parlance) barely survived with one measly Hit Point by fleeing the vicious cult who was about to sacrifice him. It fit the feel of an H.P. Lovecraft story, that's for sure.
Also, I had some ideas about Vancian magic. This is a form of magic used by spellcasters in role-playing games ever since Dungeons & Dragons first appeared, where the mage must memorize the spells she wants to cast and, once she casts them, they disappear from her memory until they are memorized again. It functions as a way to limit the amount of spells that a magician can carry around in their head at any given time, which works as an attempt to balance out what could otherwise be an overpowered character. It's also a tribute to the magic that Jack Vance wrote about in his Dying Earth tales.
It strikes me that it's hard at times to keep information stored in memory, and even harder to remember and apply it in a stressful situation like combat. What if (and this is probably already implemented in some fashion in several game systems) a wizard casting a spell when stressed has to make some kind of spellcasting roll, and the worse he rolls, the worse the unintended magical effects are (everything from the spell failing/fizzling out to a flame spell lighting the caster's clothes on fire to...)? And of course the miscast spell would disappear from the sorcerer's memory. You could take this even further, requiring the player to memorize some kind of fake magical phrase and correctly speak it for a bonus on/in place of the spellcasting roll. A generous GM could even give the mage a chance to back out of the casting with a warning ("you don't feel in control of the forces of magic this time...").
Of course, this wouldn't work with all players and/or at all tables.