These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Mega Man 2
Anti-Climax Boss: The Wily Alien is considerably easier than the Wily Machine fought beforehand. Also Wood Man, who has a fairly basic pattern even before you account for the fact that he has more weaknesses than any other boss in the series.
Even Better Sequel: One of the benchmark examples, to where at the least, the game is considered an improvement over the original in every way.
Complacent Gaming Syndrome: Most of the weapons in Mega Man 2 are very good, and the game is generally considered to have one of the better weapon sets. Of course, none of that matters considering the Metal Blade is just that broken. In fact, many players prefer to go after Metal Man first for this very reason.
Crowning Moment of Funny: Probably unintended but it's hard not to crack a smile when you consider that Bubble Lead, easily the single most useless item in the entire game (and possbily the series as a whole), turns out to be the only thing that can defeat the Wily Alien and essentially saves the day.
Crowning Music of Awesome: Virtually ALL of the tracks, but especially Dr. Wily Stage 1 (a.k.a. Okkusenman). This game has more remixed music tracks than any other game in the franchise!
Demonic Spiders: The Sniper Joe mecha-walkers. Giant monstrosities that replace the Giant Eyes from the first game. You're better off running into them to avoid fighting them — unless you have the Leaf Shield, two hits from which will destroy the walker, leaving just a normal Sniper Joe.
Game Breaker: The Metal Blade. It's a weakness to Bubble Man, Wood Man, Flash Man, Metal Man himself, and the second-to-last boss, not to mention it uses a ludicrously small amount of ammo per shot, meaning it would take a conscious effort to try and deplete it of ammo! Also, unlike any other weapon in the game, this one can be thrown in all eight directions, making it much easier to strike any Goddamned Bats. Plus it can cut through lesser enemies in a row.
The Tellys. They're small tube-like bots that infinitely respawn. Again, avoiding them unless you need resources is the best solution.
Pipis. Birds that drop eggs filled with about a dozen tiny birds that Zerg Rush you. The ones in the ladder portion of Crash Man's level are especially annoying, because they're impossible to avoid without the Leaf Shield or Metal Blade.
When the game is paused, Mega Man's vertical speed is set to zero. Repeatedly pausing the game during a long jump will make Mega Man "glide" diagonally instead of falling parabolically, allowing for much longer jumps.
When pausing and unpausing, Mega Man will be in the "teleport" animation for a split second. During this time, Mega Man is invulnerable to all weapons. This glitch is the "Time Barrage" mentioned in the "I can't beat Air Man" song.
If the game is paused while Mega Man is equipped with a weapon that uses less than one bar of weapon energy per shot, unpausing the game will "reset" the bar he's currently on, thus giving potentially infinite weapon energy for those types. This helps make the Metal Blade even more of a Game Breaker than it already is.
One peculiar glitch can be triggered during the Air Man boss battle—if you use Item 1 near the door inside Air Man's room, it takes you to a glitchy, but playable combo of Air Man's stages sprites and the level layout of Skull Castle level 2. See it in action here.
Enough objects on the screen animated at once could result in overwhelming the system's RAM, which could result in certain aspects of the game clock slowing down. In particular, a large number of enemies or a sufficiently large enemy could trigger this along with the flickering from Mega Man's Mercy Invincibility and a sufficient number of projectiles on screen. Clever use of the Quick Boomerang (easily the best for shooting many projectiles at once) could result in stretching said Mercy Invincibility much longer than it should ordinarily last. Due to differences in system architecture, this backfires in later rereleases.
Polished Port: The Wily Wars re-release, which gave the game a 16-bit graphical upgrade, remixed music and a save feature.
Signature Scene: The opening. To the point that anything that is homaging the 8-bit era has a high chance of beginning with an ascending shot of a building with the hero at the top. Even the promotional video for the Mighty No. 9 Kickstarter alludes to it.
The Buebeam Trap at the end of Wily Stage 4. Not only do you have to use Item-1 to reach the higher part of the chamber, but the boss can only be defeated by Crash Bombs, which you only get so many. If you run out, you're screwed.
Not to mention the only way to refill Crash Bomb energy if you run out, would be to shoot hundreds of impossibly placed Tellys and a bunch of Sniper Joes in narrow hallways, in the hope of getting those desperately needed energy capsules...yeah, you're better off killing yourself to restart the stage.
If you're going for a No Damage Run, Quick Man's erratic and unpredictable AI can be one of these, as demonstrated here.
That One Level: Quick Man's stage is notoriously irritating without the Time Stopper, and Heat Man's stage becomes this during the Dissapearing Blocks segment, unless you happen to have Item 2 on hand.
Among the Wily Castle stages, stage 4 easily qualifies due to its tedious string of fall-through floors and line-guided platforms. The Buebeam Trap being at the end doesn't help matters.