Free Vehicle Repair
For free and fast car repair, park your car in one of your garages, back away to let the door close, then step torwards the garage so the door opens again. The car will be instantly repaired of all dents, etc.
This is especially useful if you have an expensive modded car that you want to keep for certain ingame stats.
NOS recharge without waiting.
Instead of having to wait for the NOS to recharge to use again, exit then enter the car, and you can use the NOS again.
Early and riskfree exploration
During the mission "Reuniting the Families", you have to shoot down a group of SWAT team and then enter the motel to save Sweet. Beating the SWAT, instead of getting into the motel, you can travel all around the entire map and enter all the restricted areas like the military base and the maps that are locked. You will have no wanted level and no cops will chase you. You can explore the entire map freely without taking risk. This is the best time to confirm vehicle and item locations and to collect the snapshots, oysters and horseshoes.
Restricted areas open for you
During Woozie's mission "Amphibian Assault", the wanted level system is disabled. You can now travel everywhere in the game including the restricted areas like the Eastern naval base and all police stations without the cops chasing you. This is time to collect the two oysters in the extremely dangerous naval base without being shot.