I really enjoy Shen currently, not so much in top lane, but in the Jungle.
I have been playing him quite successfully in jungle and when your q is hitting for around 500+ dmg every 4 seconds, you have nearly 5k hp, and will kill any AD based champion attacking you, he becomes rather powerful.
Being a tank jungler and being able to 1v1 any physical melee champion late game and win the fight regaurdless of how fed they are is pretty strong.
I personally feel like most people do not use very good builds on Shen, and many use poor runes and masteries. He is unique and requires a unique setup. I pick Shen any time I encounter a primarily ad comp or when I end up with a bunch of people picking dive champs, especially
if someone on my team picks Zed I am going to pick Shen nearly 100% of the time.
I have posted this build up on a few Shen threads and while some instantly knee jerk and react by saying that build can not possibly work, nearly everyone who has tried it has reported pretty positive results.
So firstly here is the build, it in general, will be the same every game but your item purchase order would change depending. Often though you will want to build the items in the order shown, Rylia's is a potent second item as it gives you the slow on your Q a big chunk of HP and AP and gives you a nice damage bump as well as making your ganks downright lethal all mid game.

For games where you are the only tank or initiator I often swap
for
and build it early so I can land my taunts through ranged lock down. For games where they have stat shred champs like
I sometimes swap
for
but only if I am for some reason getting focused down.
For runes I run a varied setup because Shen needs a bit of everything and doesn't really have any particular strength to exploit by taking typical runes.
Yellows: First I run 9x energy regen yellows, this in my opinion, is a must as it allows you to spam your skills in most fights especially now that his taunt is cheaper and lets you use Q and W while jungeling every time they are off CDR without worrying about saving energy for taunt if something random happens.
Blues: Next I run 6x flat CDR blue with the last 3 flat MR, pretty standard. This is to round out to 10% CDR and might as well take a little extra MR since you typically won't be building an early MR item and just using your HP to tank the damage.
Reds: For reds I run 3x attack speed reds and 6x Flat Armor reds because you need armor for the jungle and in all honesty this build functions better against heavy AD comps I take some attack speed to synergize with my quints and because you need attack speed for clear times.
Quints: For quints, I run 2x Atk speed runes and 1x Flat Armor rune for the same reasons as the reds, you need the attack speed to clear your camps and with the 1 armor quint combined you end up with more starting armor than typical all armor yellows.
This gives Shen the attack speed he needs to actually clear the jungle, it gives you more armor than a standard all armor yellows setup, it gives you some MR and allows you to start the game with 10% CDR when combined with masteries and most importantly of all, if gives you that little bit of extra energy regen you need to keep spamming your Q and W in longer engagements such as 1v1 duels with tanks early game and jungle invades as well as drawn out team fights around objectives. On top of this your Q now does damage(around 300-500 every few seconds) and your shields are noticeably stronger.
For masteries I take 4-23-3 but really you can do what ever you want here as long as you take the 4 points in the offense tree for the cool down reduction the rest is up to you. I won't really get into it as most people understand getting 2% max hp regen per second when combined with warmogs and everything else in the defense tree. I put the 3 points into the run speed in utility because those 3 points really don't give you anything in the defense tree that you need and it's always good to be a little faster.
You get plenty of hp, you get ability power, you get a slow on your q which makes catching people with your taunt a lot easier, and more importantly you can actually duel enemy carries with thornmail and since you have a nearly permanent lock down with your Q and taunt, your Q combined with the Rylia's proc lets you take challenging smite so you can use your added attack speed for a little extra true damage and for reducing large AP burst damage, when someone is trying to take you out of a fight.
The teleport and ult allow you to basically farm jungle and respond to ganks so Shen's slower jungler clear times are not as punishable, you can also level 3 gank and be aggressive if laners are placing wards in a way you can teleport into when they get pushed to tower.
I am not saying it's god mode or you will suddenly becomes #LCSBIGPLAYS, but in almost every case it is better than the standard full tank randiuns build that most people run. Your Q will be hitting people for around 500 dmg every 4 seconds, if an adc or melee assassin trys to attack you they will kill themselves on your thornmail and shields, you also have enough HP,AP,and MR to stand a reasonable chance of killing many AP casters.
I suggest you give it a try if you enjoy Shen jungle, it also works in top lane by switching out cinderhulk for sunfire and I think it makes up a lot of areas where Shen feels underwhelming.