Back in the 90s, Rareware was a juggernaut among game developers, rivaling and perhaps even surpassing the great and almighty Nintendo. Games like GoldenEye, Perfect Dark, Banjo-Kazooie, Donkey Kong 64, and Conker's Bad Fur Day were just as essential to the N64's library as any of Nintendo's flagship IPs. Without Rareware, the N64 would've only been half the console it was. When Microsoft bought Rare, it was an attack on Nintendo that's still felt to this day; Nintendo lost one of its best developers, and Rare has since developed barely anything of worth on the Xbox.
Rare's presence is sorely missed, but one thing I miss in particular is how they handled the difficulty in their games. When most game developers put different difficulty options into their games, they tend just to provide the same game experience with certain statistics on a slider. Enemies deal more damage and have higher hitpoints, resources are more scarce, there might be more or fewer checkpoints, and so on. What Rare did, by contrast, was provide a completely different gameplay experience for each difficulty.
GoldenEye and Perfect Dark were both broken down into self-contained levels within an over-arching mission structure. You picked a mission from the main menu and were then dropped into the start of the level. Every time you selected a mission, it started from the beginning, with everything reset to its default, initial state. Every time you went through a mission, it would be the same, with the same enemies and items in the same locations, and the same objectives to be completed. If you failed at a mission, you'd know what to expect ahead and could plan accordingly, which made it feel like you were really mastering the game the more you learned about it.
Both games could be played in three different difficulties (basically easy, normal, and hard modes), and you could pick individual difficulties for individual levels. Besides adjusting the statistical slider to make enemies more accurate, deal more damage, have more health, and appear in greater numbers (in addition to lowering the amount of ammo drops and removing certain item spawns altogether), playing on higher difficulties added entirely new objectives to the mission as well. New objectives meant new challenges to face and often new areas of the map to explore.
As a rule, whenever I start playing a new game I tend to stick with the default, "normal" difficulty unless I know in advance that a harder difficulty would be more satisfying. I usually only intend to do a single playthrough, because with most games, replaying on a higher difficulty provides basically the exact same gameplay experience and it feels like a waste of time. With GoldenEye and Perfect Dark, you could start out on one difficulty, and once you felt like you'd gotten the hang of it, you could replay the same levels on a higher difficulty and it would feel almost like a whole new game. It allowed for the full game experience to change and evolve as you gained mastery, and it promotes practice and mastery in a rewarding way.
Even games like Banjo-Kazooie and Donkey Kong 64 that only featured a single, default difficulty could appeal to casual and serious gamers alike, because they were easy to beat but difficult to complete. A young, inexperienced gamer could get through the entire game if they wanted to, but getting every item and finding every secret was a somewhat challenging and satisfying feat even for experienced gamers. Difficulty modes are meant for gamers to be able to tailor the game experience to their interests, but with games like Banjo-Kazooie and Donkey Kong 64, you could still get as much out of the game as you wanted.
Most games these days feel a lot easier than games of the past, as if developers are trying to appeal to the lowest common denominator, and when they implement difficulty modes they often feel like a cheap after-thought that don't add anything worthwhile to the game or to the replay value. The classic Rareware games of the N64 era were great in large part because of the way Rare crafted the nuanced difficulty of their games, making them accessible while offering a lot of room for the gameplay to change and evolve as you gained mastery. I wish more games these days could implement fun, dynamic difficulty modes.
But with today's emphasis on high-end, ultra-expensive photorealistic graphics, I'm sure there's just not enough time and budget for actual gameplay innovations.