Ever wanted to unleash your ICD? Here's your chance! Become a pyromaniac with the arson mission available through San Andreas. Different checkpoints can be found around Los Santos with the following icon: 
To start the mission, just get on the checkpoint, press E and start the mission. You will be given an amount of locations to set on fire within the time limit.
Once you get to the location, go inside and equip yourself with the gas can, then start pouring the gasoline all around the area. After you've done it, you'll torch the gasoline and set the place on fire. Head to the next locations and repeat the process.
After you've set all the specified locations on fire, you will have completed the mission. Each location will give you a small bonus, and an additional bonus for completing the mission.