This is what I use on Tryndamere and I find it to work really well. But depending on the game and the enemy team this build gets moved and shifted a lot; in the order of skill, items and what items all together. I have played tryndamere for a very long time and he is a great champ. The secret to tryndamere is right click!-_- No JK. There is 3 secrets!

1. When 1 on 1 fighting both with low HP you need to be able to use your fury in the right moment because sometimes if you heal you will be able to beat the opponent. If you have 80HP while doing say 100 damage and he has 190Hp and does 80 damage considering both your attack speeds are the same and you have lets say O armor and O magic resistance you would lose because he would be able to kill you in 2 shots. But if you heal yourself just by 81 or more(Which requires little fury) you would survive the second shot but kill him. Now this sounds easy when going slowly but when facing a Master Yi with very high attack speed you would find that this is a split second move which either makes it or breaks it.

2. You need to be able to use your Ult when your HP is the closest possible to 0(In other words when your HP is at 1). This could mean life and death after your ult ends because if you wait that split second then you might swing the final blow in that split second which you waited.

3. You need to be able to use your Q or heal right after you ult ends because if you use it late your probably dead because you would have 1 hp and anyone would pretty much finish you. But if you use it early your ult naturally brings your health to 0 so you would lose some of the healing that you done on yourself. Once again that 5,10,or 40 hp could mean life and death.

Pros

+ Very high damage
+ Great healing ability (Bloodlust)
+ Great escape/tanking ability (Ultimate)
+ Can go through walls (Spinning Slash)
+ AoE Slow ability.
+ Will make the other team mad

Cons

- Can get shut down if enemy team is organized
- Can be completely useless if enemy team rush Thormail.
- Squishy early game
- Requires good timing and some skill for good use
- Dependable on only physical attacks only.
- VERY item dependant
- End game champion

For summoner spells I go with flash and exhaust. If you do this you are playing safe. I take flash because it is still a great spell to have. Flash combined with spin means you are out of the war zone and pretty much have gotten away. This is because you can cover massive distance. The exhaust is great because you are going to be doing most of the damage and if you can get in range with exhaust and your spin you will be doing massive damage as well as hitting crits. This is why I prefer it over ignite because not only will they be taking more damage exhausted but you can score crits which you obviously will not if you just ignite them.

Now you can also take ghost and exhaust but I prefer flash because you can stay in the battle what 1-2 sec longer and then flash with no health left or have yourself ghost with more health because you got Ashe shooting arrows at you.(The time it takes you to run out of her range you can just stay and instantly flash out of)

Twisted Tree Line

For Twisted Tree Line I take ghost and exhaust bemuse you can lunge over pretty much every wall on the map. This means that if you take top(which you should) you can lunge into dragon if ganked and run into jungle or lunge down to red if ganked to your allies. This means that flash is unnecessary and ghost can benefit you more such as chasing or running away if say they flashed over the wall.

I chose these ruins because first Tryndamere does not have a lot of magic resist.

I chose the health Quintessences because this gives you a very nice early game health buff which is very useful even in late game.
Another choice would be the movement speed Quintessence because this would make chasing easier and in general being faster is always great.(Movement speed is good on any champ so getting this Quintessence means you are pretty much safe to use it on anyone)

Summoners Rift

I go 24/5/1. I take all damage related masteries in the Offense tree, and put 3 into magic resist in the Defense tree, as well as the 1 into the Utility tree.

Twisted Tree Line

On the Twisted Tree Line I go 24/6/0 because I don't need the extra point in Utility and can instead put that into more armour which would benefit you much more. Now using this will mean you don't get flash. Why? Because you can lunge over pretty much any wall on the map. So this means you have and instant get away. Instead of going with flash you would get ghost because why waste a summoner spot? So this is why you then put the point from flash into more armour.

In the team fight you need to try to take out there AD carries first then the AP carries. The best way to initiate is to lunge UNEXPECTEDLY to the AD carries. This will make you much more effective. If they see you every single opponent will be going for you first. They will be focused and organized on taking you down first. Tryndamere himself has average maybe a bit lower hp for fighter or melee. You will not even notice your HP. But if you lunge form a bush they will be disorganized and will most likely no be effective vs you.

I start with Spinning Slash because this allows you to go into the bush and wait for enemy to run in at which point you can either do damage and fight or just run and lunge. Spinning Slash will provide great escape ability early on and most importantly after 6+1 minions you will reach level 2 and get his second ability.
The second ability which I get is Bloodlusht because this will allow you to heal yourself and stay in lane longer. (Not like you should need it this early but this will allow you to stay and farm longer) I then get it at level 3 again and then get my Mocking Shout.
The third ability is Mocking Shout which slows enemies which are facing away from you and LOWERS THE PHYSICAL DAMAGE OF ENEMIES NEAR BY. People tend to forget and take much more damage then they have to.
Then at level 6 I take my ult of course which makes me impossible to die for 5 seconds.

I max Bloodlust first followed by Spinning Slash and Mocking Shout as well as getting my ult every time I can(6,11,16).

TO BE FURTHER REVISED!
Comments and ideas are welcome.
Please give feed back.

I go with boots first and the 3 health pos because this gives you good get away and the 3 health pods should mean you can stay in lane longer. (For noobs, when you get ignited instantly use you health pod; it means life and death).
Then I go with the Zeal for the early game critical and attack speed. This will make it easier for you to last hit and to get your rage bar up faster for those heals.
I like to get Berserker's Grieves for max damage and attack speed. You can also go with Mercury Treads if there team has lots of stuns or more then 2 ap. And if their team has like 4 or more ad or just really strong ad then go with Ninja Tabi.
I then get a Bf Sword for more damage and later make my Zeal into a Phantom Dancer. I like to finish my Infinity Edge, but sometimes you ma need to get the Vampiric Scepter and then finish the Infinity Edge if your getting harassed out of lane.
Anyways you will get your Vampiric Scepter and and then build that into a Bloodthirster. After that you would get a Dagger and then a Bf Sword to build that in to a Black Cleaver. Sometimes I get my Dagger and Vampiric Scepter and then get my first Bf Sword of my Bloodthirster and then my second for my Black Cleaver.

For the last item it depends a lot on the situation. You would get a Force of Nature if the enemy team is heavy ap with Veigar or just has mostly ap champs. You could get a Thornmail if the enemy team is mostly ad champs. You could sometimes got for a Frozen Mallet if you want some health and the slow will make your enemies will have no chance of getting away. If the flash you use mocking shout otherwise you would just constantly slow.

It is good because I main trynd.