TechLookz

Unlockables:

Dunce Hat:
Turn on the shows in the boy's locker room.

Pumpkin Head:
Smash all the pumpkins in the boiler room.

Unlockable costumes:
Once you complete the requirements for the clothing, they're automatically thrown in your closet, in all your safehouses.

Wrestling Uniform:
Beat Gym 1.

Tiny Swimsuit: ??
At the Beach House location, find the Preppie with a blue mission on the beach and beat his swimming time

School Mascot: ??
Beat 'Nice Outfit' in Chapter 4.

Red Ninja Outfit: ??
During Halloween (must be done during Halloween) at Bullworth Academy, complete the Big Prank task

Prison Uniform: ??
Beat all the detention mini games at least once.

Pirate Hat: ??
Beat up pirate on island near Beach House.

Orderly Uniform: ??
Complete 'Finding Johnny Vincent' in Chapter 5.

Jimmy's Skeleton Halloween costume: ??
Beating the mission 'The Candidate' will open up the mission 'Halloween' which unlocks the costume.

Grotto Master: ??
Collect all G&G cards.

Green Ninja Outfit: ??
Hit stuff with projectiles (eggs, etc.) 1000 times.

Gold Suit: ??
Buy all clothing in the game.

Gnome Costume: ??
Smash all garden gnomes.

Firefighter's Helmet: ??
Pull the Fire Alarm 20 times

Fast Food: ??
Complete the Burger Joint errand found in Bullworth Vale.

Edna Mask: ??
Destroy 19/19 Tombstones during Halloween

Dunce Hat: ??
Go to the boys locker room in the gym and turn on all the showers.

Crash Helmet: ??
Place 1st in the Kart Race at the Carnival

Boxing Outfit: ?
Beat either 'Boxing Challenge' or 'Prep Challenge' in Chapter 2.

BMX Champion: ??
Complete one of the bike races.

Black Skate Shoes: ??
Travel at least 50.00km on foot

Black Ninja Outfit: ??
Fill up your yearbook completely.

Hints, Tips & Tricks:

Easy money:
Successfully complete all the challenges in the gym. You can now repeat a challenge at any time. Start one, go up to the line, then press Circle to jump. Press X to throw while in mid-jump for easy knockdowns.