Dungeons & Dragons is pretty much the gateway drug of table-top RPGs. What it does, it does well. Fantasy adventure where you go on adventures and kill monsters in dungeons.
Unfortunately, lots of folks have neat ideas which might work well with another rules system, but due to bright-eyed optimism, third party publishers trying to make bank on the D20 cash cow, or a simple unwillingness to learn other rulesets, we get stuff like this.
No-Magic Campaign: Not Low Magic, but NO MAGIC! The best weapons are masterwork, healing must be done naturally, and what spellcasters do exist have their abilities magnified by the even-wider gap from no magic items. Game of Thrones has its own RPG by Green Ronin, and Mouse Guard does this quite well, yet this keeps popping up in D&D. It is our curse to bear.
Like D&D, but better! The Fantasy Heartbreaker, so many like it, trying to edge in on an existing brand's territory. The game mechanics are more like house-rules to existing Editions adapted for the sake of familiarity rather than an eye for game design, and its incessant need to try and supersede Dungeons & Dragons means that it can't really stand on its own merits.
It should play just the same way: A lot of folks who jump from one Edition or retro-clone oftentimes carry things wholesale into a new game. This isn't much of a problem if it's done with care or an eye for improvement, but a lot of folk assume that the design decisions stayed true throughout the 40 years of history. I've seen people try to run 3rd Edition as an old-school game with no feats or wealth-by-level, people adapting 2nd Edition wilderness adventures for 4th Edition combat, and people converting old settings to Pathfinder without making changes to how the world will be impacted by the gameplay (that 1976 setting didn't have at-will cantrips or a pantheon full of cleric domains).
Even the 3rd Edition playtesters were guilty of this, missing a lot of design quirks because they played the game just like they did 2nd Edition.
Share your own terrible ideas and stories, either in person or heard from a friend of a friend!