Twitch doesn't really need an intro so I'm just going to launch into the guide.

I must note however that this is my revised Twitch build. I had one posted before and decided to take it down and reconsider it because of the comment of Xaioli and others (thanks for the constructive critism as it helped me develop a build with a little bit more survivability and spotted out how fail rushing Phantom Dancer was).

Pros:

Great carry especially when you get fed.
Ambush is amazing for escaping and ganking.
A nice slow which helps to pick off people running away.
Can scout for the team.

Cons:

Can be CC'ed.
Can be countered by oracles.
Is focused early in teamfights.

Greater mark of Desolation - Since Twitch is a physical DPS carry and relies on his auto attacks, this makes them do more damage. That's what you need on Twitch.

Greater Seal of Alacrity - Twitch relies on his auto attacks to get his stacks of poison on so these make him attack a little faster. Combined with the attack speed from his Ambush, you should be able to kill people easily.

Greater Glyph of Warding - I used to run attack speed glyphs but after realising that Twitch needed to have more survivability (thanks again to Xai) I went with his glyphs. These are sooooo good when your going against a magic based champion. Combined with Banshees Veil which occurs later on in your build, you will have lots of fun vsing a mage :D.

Greater Quintessence of Fortitude - I use these because it makes Twitch have more health which again relates back to survivabilty. You can also run Armour Pen runes but I haven't tried it because I'm to pov to afford them atm LOL.

The masteries are pretty straight forward:

21 in offense because Twitch is a carry and you want him to be doing damage. The 3 points in sunder are crazy good for twitch because they give you MOAR armour pen. I take improved Exhaust because that is one of my Summoner spells and if you don't use exhaust, put 1 in Archmage's Sawy. I get 4 in sorcery because it allows you to use Archaic Knowledge which is very good. Everything else in the tree is pretty straight forward.

9 in defense because you want to make Twitch have more survivability. I used take 9 in Utility but realised Twitch needed defense more than that (I know; fail). Having more armour means less damage and 1 in harden skin means less damage also! Having dodge is really good aswell and even though I don't have Dodge runes, this mastery makes you have more than none.

Ignite - I absoulely love this spell. I use it because it generally gets me first blood and secures kills for me with the help of my poisons.

Exhaust - I also think this spell is great. I use it on all melee dps champs. Why is so good? Well because it slows them, disallows them to do good damage on you and generally means you can kill them before they can retreat in time. Combined with your ignite, you should get first blood (in mid) almost everytime.

Cleanse - Cleanse is a good spell to have on Twitch because of the amount of CC which generally gets focused on him. I often replace this with Ignite or Exhaust

Flash - Another good spell for Twitch as it allows you to escape from ganks quite easily and even get you that kill if they are too far from you.

Ghost - A decent spell for Twitch however not the best. It can get you kills on champs running away and will save you from getting ganked sometimes but that's what your poison and ambush are for.

All other summoner spells are not generally reccommended on Twitch. You could run maybe a Heal, teleport, fortify or clairvoyence, but they aren't that great. Leave the support spells to actual support characters.

I start off with Dorans Blade because it gives you pretty nice starting off stats (health, damage and lifesteal). I then rush Boots of Mobility which is quite an important item on Twitch. It allows you to get ganks quite easily, chase down enemies, escape from ganks and makes you feel like Usain Bolt - LOL. Executioner's Calling is next up and for good reason. It gives you Crit and Lifesteal and also a nice debuff on the enemy aswell as a active dot which reduces healing. Infinity Edge is next on the agenda. THIS IS THE BEST ITEM FOR TWITCH!!!! It gives so much attack damage and makes your crits do INSANE amounts of damage. A MUST BUY. I then rush Banshees Veil because at this point, Twitch needs some survivability. After that it's Bloodthirster. I get this item because of the attack damage it gives and lifesteal. After that, I generally go with Black Cleaver or Phantom Dancer. Either one is good on Twitch but I think BC is better.

Ambush at lvl 1 because it can help get you kills whether your in mid or bot/top. Then you want to max out your expunge also getting your ulti at lvl 6. Expunge is Twitch's main ability as it does damage based on the amount of stacks they have. At lvl 8 you should get your poison before maxing your stealth with a 1 or 2 of poison along the way aswell as ulti at 11. At lvl 16 get ulti (obviously) and then finish off your poison.

Last Hitting is very important on Twitch as it allows you to get items very quickly which will aid in every other aspect of the game. It is pretty east to last hit with Twitch especially with the Gangsta Twitch skin (proest skin out). If you last hit effectivly, as it is with other champs aswell, you will be much better off.

Well, thats it for my 2nd Twitch build. Hopefully it does better than the first because it does have more survivabilty which I actually LOVE now. Thanks to all for the feedback on my other build which made this one possible.

KTHXBAI

Box :D

P.S: I LOVE WAFFLES