Level 7 mostly features Goriyas, enemies from the first two levels who aren't much harder to kill than Moblins. In addition, the boss is Aquamentus, the same boss from Level 1, with absolutely no changes.
Level 8 is this in the Second Quest. The enemy pattern is the same as in Level 7 of the First Quest and the boss is just three Dodongo enemies with four ball-spitting statues in the room (note that another room in the dungeon has exactly the same layout). While a bit harder than a single Aquamentus, it's certainly less of a challenge than the Gleeok of the previous level. That being said, the challenge of Level 8-2 is the incredibly convoluted layout, full of passageways that only take you to the beginning of the level, one way doors that force you to go places you don't want to, and a couple other rooms full of Dodongos that causes you to use up your bombs before reaching the boss.
Blue Wizzrobes. They do major damage, they're durable, they have an incredibly hard to predict motion pattern and you can't stand in front of them because they continuously fire spells if you do. And they can walk into doorways and hurt you if you stand in the door and try to snipe - you can avoid them by getting far enough back, but if you get too far back you risk leaving the room and that resets all the damage you did (these things are durable). The only strategy even halfway effective against them is to stand directly behind them, but that leaves you open to the Red Wizzrobes (see below) and Like Likes that often accompany them.
Red Wizzrobes normally are easy enough to deal with, but they become quite dangerous in their own right when combined with Blue Wizzrobes. Trying to keep your distance from the blue ones tend to result in wandering into an orange one right as they teleport into your path, as one of the only advantages the weaker variety has is the ability to teleport a greater distance (the other being their spells which are twice as strong as those from the blue ones).
Blue Darknuts. They can't be attacked from the front, they're twice as fast and durable as Red Darknuts, and they do major damage. They change direction without any warning, including reversing direction. You can be running up behind one only to have it wheel around and bump into you.
Like-Likes. They eat your Magic Shield. They also frequently show up with Wizzrobes, where losing your upgraded shield makes you much more vulnerable.
Before you get the bow and arrow, Pols Voice. Unpredictable movement pattern, exceptionally durable, immune to bombs and the boomerang, and they do major damage.
Red Bubbles, especially in the second quest. Rather than a temporary inability to use your sword, you have to touch a Blue Bubble or drink a potion. In either quest they also tend to get you killed by enemies that are primarily vulnerable to your sword.
Until you have at least the White Sword (and hopefully also the Blue Ring), Gibdos are a major pain. They require eight hits to kill and take off a solid chunk of your life. This really only applies to the Second Quest, where they are encountered much earlier than the first one.
Ear Worm: The Hyrule overworld theme and the standard dungeon theme will be drilled into your head by the time you finish the game.
Ensemble Dark Horse: The Old Man. He's only appeared in the first game (and even then he's not really in there for long), but damn if he's not the most recognized character from the first Legend of Zelda. It helps that his lines are incredibly memorable and downright weird at times.
Goddamn Bats: Keese and Gels, for being quick little buggers who don't drop any goodies when vanquished; tempered somewhat by the fact that your boomerang can kill them. Peahats, on the other hand, are completely invulnerable until they slow down and stop flying, and they have a tendency to go a long time between stops.
Good Bad Bugs: In both the NES original and the GBA edition, immediately exiting and reentering the Level 1 dungeon will somehow unlock the first door, netting you a spare key. Hard to tell if this is an unintentional bug or a deliberate secret, though it was "fixed" in the Gamecube re-release.
Paranoia Fuel: Bombing walls for secrets. Sometimes, you can find Rupee stashes, the "Money-Making Game", or other benevolent secrets. But the first time you get "Pay me for the door repair" can have you distrusting bomb-uncovered rooms afterwards.
That One Level: Level eight in the first quest and level seven in the second quest (inverting the entries for Breather Dungeon above) are full of Blue Darknuts, who are some of the hardest enemies in the game. Level 7 in the second quest actually requires you to kill no less than three rooms full of them to progress to the end.
Vindicated By History: While the first game has rarely ever been considered a bad game, for a very long time it was highly overshadowed by A Link to the Past for being the first truly great game in the series for making the series much more focused and less cryptic. Come the Seventh Generation, with the explosion in popularity of open-world games, the first Zelda has now been acclaimed by many for being an early exemplary example of the Wide Open Sandbox and for letting the player discover things on their own. At E3 2014, Eiji Aonuma stated that The Legend Of Zelda Breath Of The Wild will be taking inspiration from this game in crafting its open world setting.