A bug?

[Gyder]

You can't use a melee attack when unarmed.

[Carth]

I think the melee attack is hitting an alien with your weapon, so it's not really a bug, but it would be nice if a weaponless marine could defend themselves.

[Knight]

i dont think a punch in he face from a fist would hurt the aliens much ...
melee combat kinda refers to hitting an enemy with an object (the back of your weapon in this case)
otherwise its mostly called 'unarmed' combat

[Warskull]

"Dude, Melee attack sucks"-A marine being the last one alive, running out of ammo, and trying to melee an alien. He hit it once then it killed him.

[Pepito]

Ive seen a medic with an empty pistol Pwn 8 aliens in a row while Retreating in salvage on hard.

[Spanky]

I've also seen pigs fly. Melee works but it's nearly impossible to not take damage while you do it. Timing is key.

[Carth]

And that's why it was a medic. There's a reason why the medics are usually the last to survive.