Final Fantasy XII.
First off, if you're playing FFXII and you want to get all the items, and you don't want to be discouraged, you should probably stop reading now. No spoilers or anything (no plot spoilers at least, I'm spoiling a single awful game mechanic) but, well, you'll see why soon.
Final Fantasy XII has a really, really powerful weapon. It's the Zodiac Spear. It's the ultimate weapon. It's quite easy to get if you know the trick, and nearly impossible if you don't.
The trick is simple. You have to not open a set of utterly unmarked treasure chests scattered throughout the game. There's no way you can know this when you reach them. There's no way you can know this after you've passed them. Fundamentally, there's no way you can know this at all unless you've already read a strategy guide. I mean this entirely literally. You'll be walking through the game, and there'll be a treasure chest just like any of the other thousands you've seen sitting in your path. If you open it, you can't get the ultimate weapon. You won't get notified of this fact, either then or when you reach the place where the ultimate weapon should be. You'll just have lost out.
There is one other way of getting it. See, there's an unmarked treasure chest in a not-particularly-noteworthy location which has a 1/10 chance of appearing. If you open it, it has a 1/10 chance of having an item instead of money. If it does have an item, there's a 1/10 chance it's the Zodiac Spear. Of course, if it doesn't appear, has money, or isn't the Zodiac Spear, the quickest way to try again is to reset and return to the previous save spot.
This is crappy game design.
I'm a strong believer in a few game design tenets. One of them is that, if the game has "collectibles" of any kind, the player should be able to go back and collect everything in significantly less time than it takes to start over from the beginning. This doesn't necessarily mean that the player doesn't have to start over. Chrono Trigger had a few issues along these lines, but solved it with a New Game+ feature - once you beat the game, you can restart it with the same characters you had at the end. Needless to say, the beginning of the game goes very quickly at level 60. It does mean, however, that it shouldn't take massively more time to get the items than it takes to simply run whatever the quest is.
On top of that, major quests, like those for collectibles, shouldn't be horribly random. Player skill is important and it's something we should reward. If the player does The Right Thing, it should work - and if it is random, it should at least be easy to retry. I'm moderately fine with "go kill this giant monster, 25% of them will have the item you want", and I recognize that low-drop-rate items are an important part of the MMORPG grind (I feel that ultra-low-drop-rate non-tradable items are a mistake however - 5% of the time, give the player a token that they can eventually trade enough of in for the item) but the player should either have success reasonably quickly or some measure of progress, and the player should never ever be encouraged to punch that reset button because "it'll just be faster".
This game mechanic is punishing the player for doing something all players have been taught to do - and worse, it's doing so without informing them that they're doing something wrong. You only find out when a friend tells you or when you finally check the walkthrough to find that damn Zodiac Spear that you've never tracked down.
Bad design, people. Bad, bad design.