There's a reason why Shen's the most commonly banned champ, he's a tanky mage carry support...etc. with incredible escape and annoying shield(s), cc, and life get for his team.
Just so you know, if a section isn't filled out, it's the same as the last build.

Even though Shen's most efficient as solo top, I like jungling with him, because he sucks at clearing minions and so razors is very viable on him. His ganks are good and when you're in the jungle, there's nobody to stop your ult. Also, Shen tends to let kills slip while he's top...or he gets poked to death (and the enemy is zoning him from using his q life get).

The build seems pretty obvious until the last two items. For virtually any champ that uses ap, I like to get seeker as the last item, for the free ap and armor...then I sell it. I didn't really know what last item for Shen, I just wanted ap, so I took the largest ap item. However, I can't really use the passive well...but the same goes for every other ap item...I have one offensive spell, so rylai's, abysal, liandry...etc. won't be of much use. As for the other items, you'll notice a lot of attack speed. Not only is this good for his passive, the items themselves have additional benefits. Ruined kings gives life steal (he can't just rely on his q and warmogs), and you've probably seen a lot of Shens get rylai's, what's the point when you only have one spell to slow with? You might as well use the buffed ruined king's passive. Zephyr is becoming popular among tanks with use for attack speed, for Shen personally, it gives him cdr (super useful for his ult) and the passive means you can get tabi, which helps you a lot when jungling (esp. when you want to take a camp with low hp before you recall). The movement speed is a nice bonus. Note: You MUST get a tenacity item if you get the mastery. Shen can proc tri-force really easily, and you don't have enough cc...so there you go.

The runes are the standard mr glyph and armor seals, worth quints include health, the marks can be whatever. I would recommended attack speed or ap (not pen...you're using ap for defense)...but the point is ap/ad runes is to last hit easier early game...and since you're jungling...

All of Shen's spell help a lot when it comes to supporting, but the problem is, since he doesn't use mana, it's not worth it getting the meta support items (shurelia, shard/iceborn...etc.). You also wouldn't get utility/gold get masteries, and only one gold get item (kage)...but then you just sell it, make sure the combined price of the sell and gold mustered is more than 765 (or build it into twin shadows). I threw in wit's end so he won't be useless offensive-wise, but you can get ruby sightstone, or some cdr (kindlegem-->locket).

With all the same masteries and runes, you should get a blend of the tank and jungle items. You're summnoner spells can get ignite, ghost or exhaust.