I've never played a Mega Man game as they seem kind of bullshit but "Wood Man" is real funny.

In my circle of friends we always went after Metal Man first. His level is pretty manageable and he's a joke boss even on the harder difficulty. Play on the easier setting and you can kill him in four or five shots.

I know Brad has said pretty confidently that Air Man is always the first boss... but in my opinion Air Man's stage is a total pain in the ass. I find it better to play his stage when you get the floating platform item. And Air Man is no slouch as a boss either. There's always one of his air shotgun patterns you can't dodge. I always beat him after I get Wood Man's power.

Now, I would respect anyone who went after Heat Man first. That giant stretch of disappearing blocks was impossible for me as a child, and it still intimidates the hell out of me. I usually just use Item 2 and surf over everything.

I fight Metal Man first. His weapon is useful in Air Man's stage, and he's super easy to beat.

Usually Metal Man, but I switch it up every once in a while.

I usually go for Metal Man or Air Man.

Metal Man

Wood Man

Bubble Man

Air Man

Flash Man

Crash Man

Quick Man

Heat Man

Metal Man.

And whoever voted Quick Man is a goddamn lunatic.

Never not do Metal Man first unless you're either challenging yourself or hate yourself.

Metal Blade is the most broken thing in existence, and you can cheese yourself infinite amounts if you don't mind pausing every 3 or 4 shots. Or don't because it takes 3 or 4 shots to go down one pixel of energy anyway. Honestly, if you just use the Metal Blade instead of the the regular P Buster, you'll still probably never run out of weapon energy anyway.

Metal Man - DAT METAL BLADE

Wood Man - Metal Blade kicks his ass (and practically everyone else's)

Air Man - Weak to Leaf Shield

Crash Man - Weak to Air Shooter, and Leaf Shield really helps deal with those annoying-ass birds on the climb up.

Flash Man - Weak to Crash Bomb.

Quick Man - Time Stop takes like HALF of his health. It's crazy.

Bubble Man - Boomerangs work on him, but you might as well use Metal Blade.

Heat Man - Bubbles > Heat

@TheFakePsychic said:

Never not do Metal Man first unless you're either challenging yourself or hate yourself.

Metal Blade is the most broken thing in existence, and you can cheese yourself infinite amounts if you don't mind pausing every 3 or 4 shots. Or don't because it takes 3 or 4 shots to go down one pixel of energy anyway. Honestly, if you just use the Metal Blade instead of the the regular P Buster, you'll still probably never run out of weapon energy anyway.

Metal Blade is the complete polar opposite of broken, it's the most amazingly effective weapon in the game. (I know what you mean, but still. Metal Blade is awesome.)

Edit: I'm going to go play Mega Man 2 now.

Anyway you look at it, Metal Man is the right answer.
 
Metal Man is weak (and the only one who's weak) to your mega buster, to his own weapon, but none of the other robot master weapons. Metal Man's weapon is the weakness of three other robot masters (Bubble, Flash, Wood). Metal Man's weapon uses very little energy, meaning you can actually use this as a replacement for your mega buster(deals more damage, can fire directional shots). Metal Man's weapon is probably the most overpowered weapon in the Mega Man series as a whole due to it's practically unlimited use(really, you can pretty much whip this out at the start of a stage and through periodic energy pick-ups still have nearly full energy when facing the boss).
 
Edit: Correction, after looking it up, Metal Man is weak to Quick Man's weapon... not that it makes Quick Man preferable.

Metal Man for sure. His weapon is so versatile on most of the levels and is a really easy boss to take out with just the Mega Buster as other people have stated. I've heard others go after Flash Man and Bubble Man before since they can be taken out with the Mega Buster fairly easily.

@supermonkey122 said:

Metal Man

Wood Man

Bubble Man

Air Man

Flash Man

Crash Man

Quick Man

Heat Man

This.