Hey guys, first mobafire guide, so go easy on me.
Basically, I've seen a lot of glasscannon talon builds out there which I think are disaterous because; they only work if you're the most fed person on both teams by a lot. Talon can get focused down very hard, so here's my take on him so that you can still do that infamous burst but also stay in the fight for a lot longer.

Please note, this is a Talon Mid guide.

spaaaaaaace

Pros + Amazing burst damage. + Mobile with ultimate. + Great farmer. + Awesome harass in lane. + Very useful in team fights. + Strong counter to most AP mids.

space

Mercy Cutthroat

space

Cons - Focused in team fights. - Shut down relatively easily with Crowd Control. - Needs abilities / timing to deal the damage. - Easy target for ganks until level 6. - Needs mid or top lane to farm to full extent. - Prone to ranged harassment.

x 9
x 9
x 9
x 3

You could always swap out Greater Glyph of Magic Resist for anything else instead. Totally up to you.
In fact, I used to run with Greater Glyph of Cooldown Reduction but then realised that it was smarter to go with Magic Resistance for Mid lane along with Mercury's Treads instead of Ionian Boots of Lucidity and Greater Glyph of Cooldown Reduction for top lane.

They sort of explain themselves. 21 offense for damage output, and 9 utility because that extra movement speed from Swiftness comes in handy if you want to have that little advantage over the mid you're against so you can cutthroat over to them and burst some damage with Noxian Diplomacy + Rake.

Runic Affinity Is really useful too, because you should try to steal red buff as much as you can from the enemy's jungle. It just make it last longer which gives you far more use out of it.

mercy This is an amazing passive. mercy + cutthroat + Rake + Noxian Diplomacy + Shadow Assault = insane amounts of damage. It also procs off your allies abilities or exhaust. If the enemy is exhausted/slowed/stunned or cc'd in any way and you throw your combo at him, they're very lucky if they live.

I personally love this ability. Not only does it leave a trail as to where the enemy is running which is handy for champs such as Evelynn, Shaco, Twitch and Talon, but it also deals a lot of damage. And also gives you the ability to do something like Shyvana's Twin Bite. If you autoattack the immediately Noxian Diplomacy it gives you two attacks. Great for taking out towers or in 1v1 fights.

This is completely your most important ability as Talon. It does a lot of damage as well as slowing the target. It is also your farming tool mid - late game. You can clear whole waves with it if you're doing well enough. It is also can hit all units in a cone which makes it amazingly useful.

cutthroat This is your gap closer. Not only does it put you behind the target, but it also silences them. It is what makes Talon a scary mid because he can leap over to the champ, burst some damage, then run away without having been touched at all. You can also cutthroat to minions then Rake a champ who is running away which will slow him for you to land the killing blows.

This is just awesome. Need I say more? It gives you a 40% movement speed boost allowing you to chase or escape while also dealing massive amounts of damage to any nearby enemies. Pop Shadow Assault in team fights and all hell breaks loose.

Here's where the main difference comes in.

When you're midding Talon, you are able to get insane amounts of farm. The only hard counter I've come across for Talon is Ryze. Yes, there are others but if you play well then they're not too much of a bother.

So here's how I build him.

Start Boots, 3 Health Potions. Last hit minions while harassing whenever your match comes close enough for you to hit with Rake. This usually scares them after level 4 because of the damage it causes. Boots are really good to start with because it gives you a movement speed advantage for dodging a skillshot, or to chase them down.

Assuming you know how to farm well, you should be able to afford Mercury's Treads easily before level 6. (If you get first blood, that's even better. Throw a Vampric Scepter in there too.)

Mercury's Treads will give you a crazy advantage over any mid. Reduced damage if they're AP and reduced CC. This will allow you to keep farming and harassing without being bothered too much. Be sure to get a suitable amount of ganks, because Talon works very well with most junglers. Noxian Diplomacy, Cutthroat, Rake and they will be at half or below hp. Then you and the jungle can finish them off.

Assuming you manage to stay in lane safely for long enough you'll be able to afford a B.F.Sword. Get that and continue your endeavor.

By this stage there will likely be roamers, but your damage output will be pretty damn decent. So just keep farming and pushing. Get a few hits on the tower, then repeat. If somebody tries to get you from behind when you're at the tower, Cutthroat to them and run away. Never fails. if from infront, slow with Rake and run away.

Next comes Bloodthirster. You know the drill with that, farm it up and let all hell break loose.

Depending on how well your team is going, you can decide to get a Frozen Mallet or Last Whisper first.

Frozen Mallet is good if the enemy does quite a bit of damage, it also gives you a slow for chasing.
Last Whisper is good if you're pub-stomping and want to get through the armour they're building to stop you.

After all this, you'll likely be focused in team fights because of your insane amounts of damage. So build up a Guardian Angel. This item is one of the best items for any assassin.

Then, if the game drags on any longer than it should, get an Infinity Edge. You'll be completely unstoppable once you get this. Even if everybody has finished their builds.
You could always take a Trinity Force over Infinity Edge, however I find Sheen's passive useless after early-mid game. And you already have the slow from Frozen Mallet, not to mention attack speed is useless on Talon. So that's why I take Infinity Edge instead because it gives you far more damage and is far more useful.

Always roll with Flash on Talon.
It gives you an edge if you want to chase somebody, Flash + Cutthroat covers a huge amount of ground.

And Ignite is just really nice for that 5 extra damage with Summoner's Wrath , and the true damage it comes with. I always cast it before I use abilities against the person I'm planning to kill.

You could swap out Ignite for Ghost, as Ghost works well with Shadow Assault because you remain invisible after using it.

Exhaust is another one you could swap with Ignite, but Rake works just as well so it's nicer to have the true damage from Ignite.

In team fights, your job is to take out the carry. Usually it's a ranged AD carry.

Anyways, here's how I do it:

Flank the enemy if at all possible, and Cutthroat to their carry who will likely be at the back. Ignite them, use Noxian Diplomacy, then Rake them and their allies. As soon as they realise what's going on, pop Shadow Assault and the carry should be dead. Run down the middle and towards your teammates who will be in the midst of the team fight then release your ult and do more damage. Now you're good to head back in and autoattack + + .

If you're teamfighting at baron or at their base (bad idea, but it happens) flash in then Cutthroat to their carry. Follow previous steps. With the Frozen Mallet and Guardian Angel you can afford to make risky plays like this. Just make sure you focus the one person and not hit the tank. Mercury's Treads are just fantastic for any CC.

Or if you're late to the party because you were pushing a lane or something, dive into the carry once again using Cutthroat and pop Shadow Assault twice to burst massive damage to all the enemies. I've gotten a penta like this.
;o

The times I remember to screenshot it before hitting the play again button are below. Usually remember because I go 0 deaths, and the enemy surrenders before the fun starts.
But, here you go.

So yeah, this is a really different way of building Talon, I know.
But I carry 8/10 games using this build.

Even though it seems silly, it really does work.
So please, try it before you judge it.