Anyone who has run Call of Cthulhu for any great length of time will no doubt be familiar with the "D&D Effect" - the phenomenon that occurs when you get someone at your table who is used to D&D-style gaming that tries to play CoC for the first time. Weaned on a steady diet of beneficial magic items and cool powers, they tend to approach CoC in a very headstrong fashion, assuming that the combat system is there to help them solve their problems or get them out of trouble (hah!) and that moldering tomes and eldritch artifacts can be harnessed to their benefit (double hah!). Watching someone suffer from the D&D Effect can actually be fairly entertaining from the Keeper's side of the screen, especially when the headstrong player starts fiddling with Things that veteran players wouldn't touch with a ten-foot science pole.
The funny thing is that my current face-to-face group is made up of just such a group of veteran investigators who much prefer to solve mysteries than to throw down with fisticuffs (or worse). I'm currently running Deadlands: Reloaded for the group and, two sessions in, I've noticed a curious phenomenon, the reverse of the D&D Effect, in fact. Call it the Cthulhu Effect; it's what happens when you put veteran CoC players into a campaign that assumes a high level of rock 'em, sock 'em, two-fisted action. So far, both sessions have concluded with opportunities for epic combats. The first one kicked off with the group hiding under a (stationary) train until they were eventually compelled to act (and proceeded to kick ass, much to their surprise). The second session saw them fleeing for their lives from a fanatical, angry mob. (Granted, that decision was probably the better part of valor, but they didn't even try to fight before legging it.)
They're cottoning on that Deadlands demands a somewhat more proactive approach than CoC, but it's been an amusing process to watch. I feel like saying, "Guys, you're armed with Gatling shotguns and mad science tech - you're not neurasthenic New England professors anymore!"
(One last semantic note: I realized as I wrote this that the "best practices" of a group of Cthulhu investigators apply equally to a group of old school D&D adventurers: treat everything as if it is cursed, a mimic, or otherwise out to get you. But saying "the post-3e era D&D effect" doesn't have quite the same ring to it. Apologies to all you old school D&Ders out there for lumping you in.)