I must say, and I think you'd agree, that the cosplayers are getting REALLY GOOD! I came across the following bunch which I thought were great and must be shared.
Staring with the Batman Family:
Batman's future version, Batman Beyond
Batman's most trusted lieutenant, Nightwing 
The one who broke the bat - Bane (female version)
Meow - need we say more?
Batgirl, or should I say Oracle?
Another of Batman's most trusted lieutenants, Robin.
Why so serious?
Almost as crazy as her idol, Harlequin.
Soon to be on the Big Screen, Wonder Woman. This one looks GREAT!
(Dark?) Supergirl
DC's biggest Bad@$$ Deathstroke
Hmmmm.
Star Sapphire. Double hmmmm.
The Comedian (female version) from the Watchmen.
Now we go to the Marvel guys.
Victor Von Doom once said, "Pain is for lesser men."
What is it about super-heroes falling for Cat-themed females? 
Classic Hawkeye.
Mystique, movie versions.
Mystique, movie versions.
Psylocke, hopefully, we'll see her in an upcoming X-Men movie.
We all know the Black Widow from the Avengers.
Gamora, most recently seen in Guardians of the Galaxy.
Elektra, from Daredevil or her own movie.
And then we have a few Non-Marvel/DC characters whom I thought also look fantastic.
Kratos, from the game God of War & Hellboy from Dark Horse Comics
And now, some of the femme fatales:
Ariel, the little Mermaid.
Elsa from Frozen.
And Jessica, the wife (yup, you read that right) of Roger Rabbit.
