Hello fellow Summoners! Welcome to the first in what i hope to be a long series of interesting new ways to build everyone's favourite champs! In these guides I will be suggesting build paths that to be reasonably effective, so don't worry, no Riven Support will ever be shown here.
Feel free to comment on these guides asking for me to cook up a build for a champion, or even suggest builds to investigate. I hope you have fun using these builds on the Rift!.

On-Hit Twitch hopes to make our stinking hypercarry rat into a massive tank shredder. the aim of the build is to make use of a whole wide array of on-hit effects, ALL of which are procced by Twitch's ultimate. Rat-Ta-Tat-Tat. This means Twitch loses some of his ability to duel other Marksmen, but he gains much more damage against tankier targets so he can safely shoot through whoever he pleases in a team fight and still provide good damage.

Abilities

Deadly Venom
Twitch's auto attacks apply a true damage poison stacking up to 6 times. This passive makes your AA harass more potent, and it's a good idea to get this stacked. A cool trick you can do is apply an auto attack, wait 2-3 seconds, then apply another attack to refresh the poison and add another stack, or use Venom Cask if they move out of auto range. This means the poison will deal significantly more damage over time, and make it difficult for many melee champs to handle you.

Ambush
Your main escape tool. The Movement Speed and stealth means Twitch can enter stealth then suddenly move in another direction for some sweet jukes. The problem is that Ambush takes 1.5 seconds to activate stealth, or 6 seconds if you remain in combat. As such, you will need to gauge when your opponent is starting to go in, if they use any mobility abilities, like Riven with Valor then pop Ambush preemptively before they reach you. You can then use the Attack Speed buff from exiting stealth to counter attack. Save this for enemy engages.

Venom Cask
This spell can be used 2 ways. Agressively, you can use this to refresh Deadly Venom's poison and apply 2 more stacks for bonus damage. defensively, you can toss it on enemies trying to get to you to slow them allowing you to kite and fight, or use Ambush. How you use it will depend on your opponent and the general state of the lane.

Contaminate
Twitch's main burst spell. In lane, be wary of spamming this to much, as Twitch can run out of mana quickly if you use abilities to much, so make sure to only use Contaminate if it'll be efficient. Use this when trying to clear a wave that's been pre poisoned by Venom Cask, or when your lane opponent has 3 or more stacks on them.

Rat-Ta-Tat-Tat
The cornerstone of this build. In lane Twitch's ultimate doesn't help much as most lane matchups will discourage you form getting close enough to make full use of this, you'll only really use this to win certain duels, or to get the extra range to finish a fleeing foe. Once laning is complete, stay on the back line, wait for your team to initiate, then start killing. Don't be too picky over who you target, as the piercing effect of the shots, as well as your on-hit effects will means anybody in the shot's piercing range will take some decent damage, so don't be sad if it's only safe to pierce through their tanks. One thing to note is that the bolts can actually pierce through targets and travel BEYOND Twitch's shot range, meaning you can pick off far off targets by shooting through other enemies between you and the weakened foe.

Blade of the Ruined King - A staple item on ADC Twitch, and a staple item here. BoRK has a 8% current health on hit effect, making it a good first item against high HP champs like Cho'Gath or Sion. The lifesteal helps you sustain in lane, and the active can save you in a duel, always grab this first if you can.

Black Cleaver - Did Riot know how good the new Black Cleaver was gonna be for this build? The armor shredding passive means getting max stacks with it also leads to max stacks of Deadly Venom for TONS OF DAMAGE. The health gives you some much needed survivability, and the CDR allows us to have our game changing ult up more, and helps us spam Contaminate more.

Wit's End - Twitch's favourite stat? Attack Speed. What does Wit's End give us? Attack Speed. Beautiful. The on-hit Magic Resist steal is better for making YOU tankier, since no one with half a brain is going to build Magic Resist against you during laning. This item helps you shred MR off for our midlaners though, and it functions as an excellent first item against magic damage heavy opponents, most notably Rumble and Teemo.

Frozen Mallet - Do you want to chase people for a million years? DO you want to kite like a little ****? THEN BUY FROZEN MALLET! This item helps us in teamfights by making it harder for our enemies to escape, and harder for them to close the gap on us so we can shoot them more (huzzah). This shouldn't be your first item unless you are against a high AD threat or lane bully like Riven or Yorick. The 700 Health is a god send.

Berserker's Greaves - You could honestly buy whatever boots will work best, so use your better judgment. These boots are generally the best simply because more Attack Speed means we proc our on-hit effects FASTER. The Homeguard enchantment is very useful, especially if you run Teleport.

Bloodthirster - 20% Life Steal on Twitch is beautiful,and the 80 Attack Damage gives us a fantastic groundwork of AD on which our on hit effects can go to town. When you get this can vary massively. Against high sustain matchups like Vladimir you can rush this to keep up in HP, but otherwise make this one of your later items.

Runaan's Hurricane
- Applys Twitch's various on hits to multiple targets, improves your teamfighting and splitpushing, if any of the other 6 items is not appropriate, Runaan's has much to offer, as well as MOAR ATTACK SPEED!!!!

Deadly Venom makes Twitch a potent lane bully, especially on melee champs
Contaminate is good for waveclear and extra harass damage
Ambush is an excellent escape tool, and allows for counter attacks
Rat-Ta-Tat-Tat procs all on-hit effects in this build
Excellent in teamfights
Very strong against tanks, especially those with low sustain

Venom Cask has an underwhelming slow
Ambush needs good timing to activate stealth otherwise Twitch can be caught
Laners with damage and sustain like Fiora are difficult matchups
Laners with numerous gap closers like Diana are hard counters
Mana hungry
Very vulnerable while Ambush and Venom Cask is on cooldown

Allow me to describe an full build On Hit Twitch looks like.

After 6 auto attacks Twitch will have.

Dealt 1500 in AD damage (not including Armor)
Slowed targets by 30%
dealt 252 in magic damage (not including Magic Resist)
Stolen 25 Magic Resist for himself, and leeched up to 25 from targets.
Shredded 30% of a target's Armor
Dealt 8% current health per shot.
Healed for 300 Hp from Lifesteal

He also can do this ON THE ENTIRE TEAM. Rat-ta-Tat-Tat pierces units and applies all on-hit effects, with the exception of reduced lifesteal, so you can proc all these effects on several targets, dealing impressive damage and softening any survivors up for the rest of your team.

The first thing to do is to focus on getting that first item, whether it be Blade of the Ruined King or Black Cleaver, or whatever. Make sure to get as much farm as you can early on and don't be afraid to back early for an item.

Secondly, make use of the fact you have a poison passive, make sure you harass your lane opponent whenever they try to farm to try and poke them out of lane, otherwise most top laners will happily jump on you and kill you. Use Contaminate whenever you get 3 stacks or more of Deadly Venom, and use Venom Cask when in a favorable trade to add 2 more stacks of poison to reset the poison's duration, and increase Contaminate's damage when you use it.

Finally, while the point of this build is to build all of the on-hit items shown, you MUST build them in a different order depending on your lane.

Thank you for reading my guide to On-Hit Twitch! Feel free to comment on the guide to let me know what champion you want me to find a Totally Viable build for!