Most games I would get a Void Staff instead of that second gunblade. You need some mPen options in your guide.

I disagree on the Burning Embers vs Tenacity thing. You can get that 10 AP from runes or something instead. Tenacity is much more useful all game long.

I actually use 16/0/14 masteries on Akali. Maybe you could add some alternative trees?

Alternative masteries, items and summoner spells would also be great.

Check out jhoijhoi's Guide about Making Guides for some formatting tips. I encourage you to read the whole thing; it will make your guide a lot better.

Upvoting to counter troll vote. Add lich bane!!

Me I think you should take a trinity force at the place of a rabadon because its give even more ad and make you a real assassin

lol

Very solid build. However, only thing I would consider adding is a Lich Bane. I've posted this on nearly every Akali build that doesn't include one. The item is simply too valuable to pass up on. Sure, people get all frownyfaced when they see the mana, but they never realize the true beauty of its passive. It gives Akali MASSIVE burst, and is most certainly a good investment.