Everything that counts toward the in-game 100% stat in Vice City Stories: 59 story missions, the full criminal empire, 99 red balloons, all rampages and unique stunt jumps, the vehicle missions, time trials, races and challenges.
There is no official point table. Weights follow the community checklist for the PS2 version: 240 equal objectives (about 0.417% each), the superset of both versions. The PSP version has 223 (about 0.448% each): it lacks 5 rampages, 6 unique stunt jumps, 5 checkpoint challenges and Rush!, which are marked "PS2 version only.". Red balloons count once per 10 popped; completing all rampages and all stunt jumps each gives one bonus objective.
99.6% quirk: the 100% reward is granted at 99.6%, so one objective (usually Skywolf) can be left undone.
Missable warning: build a High Roller Drugs business before Hostile Takeover, or its percentage is never awarded, and do not take over every empire site before From Zero to Hero, which unlocks the Drugs, Smuggling and Robbery businesses.
Reward: infinite ammo and cutscene replay at the Clymenus Suite; on PSP, all multiplayer content.