This is a build that I made up as I got to play with Tryndamere, it is very good but requires time to finish.

With this build you can:
Solo the Baron without losing much health
Get massive multi-kills
Jungling with ease!

Pros:
Lots of Crits=Lots of Damage!!!

Nice Lifesteal= Almost die, no problem, just attack a few minions and your back at full!!!

Cons
Early game may be bad because Tryndamere is VERY item based

Tryndamere will not have much armor so he is vulnerable to group assaults (Although he may kill the group too :D)

They will run away from you, this may prevent multi-kills, just may (EXHAUST BWAHAHAHAH)

Abilities:
Bloodlust: Miniature heal, won't really help much, I don't use this that often

Mocking Shout: Its a slow if their facing away from you. This is VERY helpful, use this with spinning slash

Spinning Slash: You spin forward towards where your going. This is very useful for attacking and escaping, you should use this the most

Undying Rage: When you're about to die, this gives you 5 extra seconds of life and replenishes a bit of your health, use this when you need it, like when you NEEED it!


Tryndamere's skill sequence is mainly based on his spinning slash because it will help you kill a lot of your enemies.You should definitely get the mocking shout early to help you and your team-mates get some early kills.

First, pop out and start attacking them with your team-mate, as you attack, he will run away, use mocking shout to slow him and attempt to kill him with your spinning slash.

In the case he is next to/behind a turret, save your spinning slash and spin through the turret because, with his spinning slash, Tryndamere can go through walls and buildings. When you do that, start attacking again. The turret will damage you greatly, and this is not recommended if you are fighting two people (if one is dead you can), but if it does too much, try to use your ult, undying rage.

My item choices are mainly based on critical strike and attack damage knowing that Tryndamere's fury gives him crits.

=EDIT= You do not NEED Avarice I only get it if I think that I ain't going to get built

Early Game:
Item for Avarice Blade + Potions
Returning From Lane:
Avarice Blade + Boots of Speed

After that just try for the Berserker's Greaves and you can now start the build.

Start with one Phantom Dancer of which will give you some crits (May help you)

Then, get a Bloodthirster which gives you lifesteal (You can start jungling)

After that, get an ionic spark (For jungling still)

For the last main item, get an infinity edge which will give you an edge (lame joke) because it will allow you to do more crits for more damage

Those are the main items you need, now you can get the extra items to give you that OP Tryndamere that everyone wants to use.

Start with another bloodthirster because that allows you to stay alive longer (Even if you are at low health, just farm some minions and your at full again!!!)

Finally, get another phantom dancer which will give you a massive chance for crits and perfect your build!!!!


Substitutable items: (Exchange one or the other)
Ionic Spark: You can exchange that for maybe another phantom dancer or infinity edge

One of the Phantom Dancers: You can exchange that for maybe an infinity edge because it will still give you 100% crits with all of your fury!

Use this build on possibly:
Master Yi
Warwick (for jungling purposes/Baron)
Maybe Gangplank (Haven't played with him for a while!)