Not Updated For Current Season
Yes it is a troll build and it is amusing. Plus Soraka has a base attack speed of 0.9 at level 18 so it's funny.
Masteries: 9/0/21 (Flash, Greed, Clairvoyance)
Summoners: Take a good guess (Flash, Clairvoyance)
Runes: Armor Pen Marks and Quints (yum)
Items: Nashor's, Rageblade, Boots of Lucidity/Mobility/Berzerkers (depending on CDR Runes), Malady, Aegis, Starks or Black Cleaver.
If you have lots of money you could try a Trinity Force, Frozen Mallet, Phantom Dancer. Why not?
Skill priority remains R > E > W > Q, with an early heal. Remember your heal gives you a good amount of armor so you can afford to be more aggressive early game. Lots of people do not expect Soraka to be running Armor Penetration runes so you will be doing about 55-60 damage a swing.
The reason to get ability power items first not to give away to the other team you have armor penetration and are going to be building attack speed. Until they realize your itemization in early-mid game.
Go troll. Spam Q. Heal team mates, Silence casters. Bust out your Wish at 8 stacks to turn the tide. Troll harder. Hit turrets.
If you really want to troll, drop Clairvoyance for Ignite. Heal yourself, auto attack some, Flash, Ignite, Infuse, Attack can sometimes land you first blood with Soraka or your lane partner.