[nq:2]Mancunian[/nq]
[nq:1]And, more recently, in a slang usage - 'manc' (which also does service as a noun)[/nq]
There's also 'Manky' - vaguely **** - "Bad, inferior, defective; dirty, disgusting, unpleasant" (OED) which I've always thought was derived from cheap goods manufactured in Manc, though OED doesn't agree with that etymology...
DC Manc resident, but Sotonian, not Mancunian.