-Massive burst damage
-Insanely good chaser
-Actually helpful in team fights if handled properly
-Very suishy until you get a Giant's Belt
-Easily harassed by the right champs
-Anyone cheeky enough to buy an Oracle's will reduce your Twilight Shroud to a really bad slowing mechanism
Since the new energy runes haven't been added on here yet, I'll just mention which runes I've been testing in here. The best combination I've tried thus far will be four static energy/5 runes with four energy/5 per level runes. Any combination is acceptable however. These little beauties really do help with end game team fights, so it's worth the extra IP.
Here's a break down of how to purchase item parts to maximize your damage while you're saving up money.
Rylai's- Buy the Blasting Wand first, then Giant's Belt, then the Rylai's upgrade. If you're getting hammered early on, Giant's Belt first is a viable option. After all, you can't kill people if you're dead.
You will always want to max out Mark of the Assassin first. It is your harass tool and the source for most of your damage. Twilight Shroud will be your lifesaver should things turn for the worst during team fights or solo ganks. Maxing Twilight Shroud out as quickly as possible is generally a really good idea. However, if your opponents are of a less than adequate nature, switching out Crescent Slash for a few of the early Twilight Shrouds can be a good idea. Crescent Slash if pretty self-explanatory, so I won't go into it at all. Shadow Dance is your baby though. It is your assassination tool, your escape mechanism, and the main reason Akali is so good at chasing. When you start attempting solo ganks, make sure you have at least 2 Dance charges. Unless the target has incredibly low health, 1 charge will not be enough.
Early Game/Laning Phase
It should be noted that with Doran's Blade, your runes, and the 21 point offense mastery both your passives are activated. Congratulations, you are, with the exception of a Red Pot Shaco, the hardest hitting champs at level 1. You have ~70 damage and 20 AP and 630 health. You are a force to be feared.
Your ultimate goal during this phase is to live long enough to get your Boots of Speed and at least the Giant's Belt before laning ends. Truth be told, this isn't overly difficult. It simply requires you to not be stupid and avoid taking ridiculous risks. Given enough time, the other team will inevitably make a mistake and it is then that you capitalize.
General laning procedure is to last hit minions for the gold and harass the enemy champs as much as possible. If you're laning with a champ that has a stun, try to set up ganking opportunities. If you're laning against a champ that has a stun, try to avoid giving them ganking opportunities. If you harass against a champ with a stun, drop a shroud as often as you can so that it will cover you should you get stunned. Popping Twilight Shroud will more often than not just make the enemy run away from their creeps. If this happens, kill their creeps. We're in this for the money, so get a few creep kills for some much needed gold.
Continue to harass and last hit minions until laning ends. If you've managed to stay alive through the entire phase, you'll hopefully be well into a Rylai's.
Mid Game/Ganking Phase
The ultimate goal of this phase is to strike fear into the hearts of your enemies. Nothing accomplishes this faster than nuking a few champs down before they have time to react. If you see an enemy alone killing minions, or whatever they might be doing, don't be afraid of going over to say "Hi!". Just make sure to scout a little bit before attempting a kill. Also, try to avoid solo ganks if the enemy team has a champ with a global teleport. You'll just be slaughtered for you efforts. If your adversary is getting away, let them. Chasing down a champ you have no chance of catching just gives the other team time to get a trap set up.
This phase is, however, made much easier once you have your Boots of Mobility. Your boots essentially become your secret weapon as far as your items are concerned. Using Imp. Ghost with Boots of Mobility means that you can change lanes very quickly, catching unsuspecting prey completely by surprise. Chasing is made even easier with this combo as well.
Team fights are slightly different for Akali when compared to other champions. Most Akali's will run in just after the fight has started and attempt to do something, anything, but will inevitably die for their effort. The trick to team fights as Akali is to pick out the other team's Carry and nuke them down as best you can before they or their teammates realize what you're doing. Once their Carry is down, or too scared to stay in due to low health, run off again. One of a few things will happen. A, the Carry will haul as much *** as they can back into their base to heal, B, they will be dead, or C, your enemies will chase after you, giving your team time to kill anyone that was distracted by you. Any combination of the previous options is possible as well. Running for your life is generally how this tactic ends though. But, even if you die, you've done your job. You've effectively removed the other team's Carry from the fight and have given your team a fighting chance at winning. Always try to circle around and help with clean up though. Health permitting of course. Rinse and repeat as many times as necessary.
End Game/Base Phase
As long as you've followed this guide, you'll be able to nuke down anyone, minus Tanks, within a few seconds. Your Akali is also a pretty effective turret killer. She does, however, still need someone to tank it for her. Minions and your team's tank can help with that.
Team Fights at this stage of the game should be handled in the same way as Mid game.
I hope you've enjoyed my guide. Feel free to ask any questions you might have.
Note- This build has been thoroughly tested with great success in practice games and normal queues. I would also like to add that your AP will be higher in game with this build. You will end the game with ~450 AP instead of what's posted. You will end with less health than is posted as well. I think you end up with ~2900. Also, a big thanks to my good friend Yossarion for putting up with my endless practice game testing sessions.