This extract is taken straight from my 100% completion walkthrough that is posted on this site: Check It Out!
100% Completion Rewards:
As I said before, well done for completing Grand Theft Auto: Vice City, here are you?re much deserved rewards:
REWARD #1: 200 Health and 200 Armor.
REWARD #2: Every vehicle you drive has become twice its usual durability.
REWARD #3: Infinite Ammo for all weapons.
REWARD #4: The Frankie outfit is unlocked at the Vercetti Estate.
It says on it:
"I Completed
Vice City
And All I Got
Was This
Lousy T-Shirt"
REWARD #5: Three Bodyguards are unlocked in the Vercetti Estate (the western
room on the first floor-the TV room). They'll follow you and shoot any person
you lock onto and fire at. Step into the pink marker beside each of them to hire them--spending $2,000 for each one.
REWARD #6: The Hunter is unlocked on the helipad in Ocean Beach. It's on the southern end of the east island.
REWARD #7: An Armor pickup and the Python (PS2)/.357 (PC) are unlocked in the TV room of the Vercetti Estate.
REWARD #8: The "Vercetti Gang" carries Uzi 9mm?s becoming the most powerful gang in Vice City.
REWARD #9: You get phone calls from Kent Paul, the Colonel, Ernest Kelly (Print Works), and Steve Scott (Film Studio).
Hope this helps!