The first idea that came to mind when I saw your question was ComicCon! I don't know an event on the planet that has so many stunning cosplay outfits all in one place.
Here are some examples of outfits you can take inspiration from.
Wonderwoman
No comic book convention would be complete without the DC superheroine and her lasso, so this is one cosplay costume you will always see at Comic Con.
Catwoman
Similarly, catwoman is another stalwart in the cosplay world. With the shiny catsuit and a trusty cat o' ninetails - this outfit is also great if you're planning to go to an S&M afterparty!
Lady Nightwing
Whilst we're on the dark side - this outfit is definitely worth a look:
This get-up is also a great example of how a simple weapon can add so much to a cosplay outfit.
Speaking of weapons...
The 'gal with guns' look is another classic that you may want to explore. My suggestions would be to go with a piece that's more Halo than Kalashnikov, unless you're really into Counterstrike (or Al Qaeda...)
