Hey guys.
Had an idea for a Thresh build that has been testing way too well for me. I won't hog all the fun, so try it out yourself.
Flat AD reds
Flat Armor yellows
7 scaling MR blues
quints + 2 blues flat CDR (=6%)
Masteries are 19/11/0
Offense: 4% CDR, summoner's wrath, 5 armor pen, 8% armor pen, 8% magic pen and spellblade
Defense: All the health, +5 armor and +5 MR
Flash / Ignite
Start with whatever items you want and take Q first. Support bot but think of Thresh as a kill-lane partner rather than a support. Spend time harassing the opponents. Don't expect the Q to pull the target so much as suppress them for 1.5 seconds.
Here's the early build:
Boots
Flask
Phage
Then rush Spirit of the Elder Lizard. 
This looks weird but it works so well on Thresh. The burn from the SEL will be added to all three of his damage spells as well as his auto-attacks. Combining this with his passive makes him very painful to be around.
The mid build:
Merc Treads
Flask
Frozen Mallet
Spirit of the Elder Lizard
He becomes a off-tank/bruiser/utility/support/dps. His AD climbs to 185, he slows and burns near constantly.
End game:
Merc Treads
Frozen Mallet
Spirit of the Elder Lizard
Abyssal Scepter
Frozen Heart
optional item - Will of the Ancients/Ruby Sightstone/Blade of the Ruined King/Hurricane
The optional item can be anything you like. The rest of the build makes it really hard to kill Thresh. He also becomes a double aura against the enemies. (since he can pull into them) He also hits max CDR, which really helps with his fairly long cooldowns. (especially his ult)