Has retro charm, but also some problems.
Melee Man (who, as many people pointed out, paradoxically uses a gun) is a fun and challenging retro game that takes heavy inspiration from Megaman. There's something inherently enjoyable about shooting little pixel enemies and getting a key to get past a level without the artsy graphics or complex story. It's simple, safe, and nothing anybody hasn't seen before. Pretty basic, and it works very solidly without many glitches.
My one major gripe is the boss fights.
Oh man, the boss fights.
There's only one boss, and he's a combination of a meme and a Newgrounds icon. You fight him something like three times (I only got to Level 15 thus far), and his attacks never change. He throws cannonballs at you, and when you deal enough damage, he gets angry and throws a whole lot more cannonballs at you. It's not even a good boss to begin with - I expected it to be a joke boss, but got a sinking feeling when the bastard showed himself again - and making us fight it more than once is cruel. Plus, the later installments can get frustratingly difficult, with the player being surrounded by bottomless pits and the boss having a nasty habit of teleporting right above your head.
For the most part, Melee Man is solid. It doesn't try to be original, and it does what it's meant to do - provide us with good ol' retro Megaman shoot-and-run fun - admirably. If you decide to create a sequel, however, work on those boss fights.