Edit: Never mind, they do respawn. *PHEW*
Edit II: I'm on 85.5% and all I need to do now are:
Story Missions - 60%
Complete all 90 Story Missions.
Complete 4 Procedural Missions - 8%
Little Jacob's Drug Delivery - 2% Complete
Brucie's 10 Car Exports - 2%
Brucie Races - 2% Complete
Assassinations - 2% Complete
Car Thefts - 2% Complete
Deliver all 30 vehicles to the garage.
Friends - 10% Complete
Open all unique abilities and complete all activities (except for Roman & Dwayne).
Activities - 5% Complete
Beat computer or Friend at all activities once:
Darts vs friend or computer win - 1.25% Complete
Bowling vs friend in a FULL round win - 1.25% Complete
Pool vs friend or computer win - 1.25% Complete
QUB3D beat high score - 1.25% Complete
Random Characters - 5% Complete
Find all the RCs and complete their encounter missions (except Jeff, Cherise Clarence & Ivan)
Most Wanted - 2.5%
Kill all 30 PEDs on list
Vigilante - 2.5%
Complete 20 crimes (don't need to be done continuously)
Flying Rats - 2.5% Complete
Find all 200 pigeons.
Unique Stunt Jumps - 2.5%
Complete all 50 jumps.
Total = 100%
Which will leave me on 95%. I've met 13 RC's excluding Ivan because I killed him, but he doesn't count towards the 100% anyway. There has to be something else.