I thought I'd make a topic listing all the things I do when I'm bored.
1. Activate the "Cars fly" cheat. Jump on a random car, start shooting at pedestrians. Don't shoot at the car, most people get out and start beating you with various objects. If you're on a good stretch of road, the car will eventually start flying. Make sure you have the parachute. It usually takes me awhile to get in the air, but it's fun. After you're in the air, shoot rockets at cities, police helicopters, kill the guy driving etc.....
2. Activate the "Cars fly away" cheat, that makes cars start flying when you bump into them. Get a car, park it somewhere, get another car, position it in front of the other car. Then carefully nudge it, the other car will fly up very slowly. Get out, spawn a jetpack. Fly onto the car, and release the pack while trying to stay on the car.
When you're on the car without the jetpack, pull out your shotgun and fire it at the front end or back end of the car, the car will start turning in mid air. See if you can keep your balance. Keep in mind though, that after awhile, the car will explode due to all the shotgun blasts. You can also try throwing remote explosives on it to make one end heavier, but you'll run out eventually.
3. Activate the "Cars fly away" cheat. Get a bike. Jump the bike and make it land on the hood of a car, the car will start flying away. Try and keep your balance and see how long you can stay on. Don't get off though, the bike usually falls and you slide off.
4. Fly the Vortex. Activate the "Cars fly away" cheat, then spawn a vortex. Steal a car and drive up to the Vortex without touching it. Spawn a jetpack outside the car, then get back in. Carefully nudge the Vortex. It'll start going straight up into the air. If you hit it too hard, it'll spin and start rotating which is not good. When it's flying, get out, and get into the jetpack. Fly up to the Vortex, land on it, and exit the jetpack. CJ should try to enter the Vortex, but he might miss a lot. Depending on how fast the Vortex is flying, he should take 4 - 5 falls before he splatters on the pavement. When you finally do get into the Vortex, you can fly it around like a car, it'll steer and go up and down though it's kinda hard. If you don't do anything, you can get to the highest altitude.
For more fun with this one, do it on two player and when you're in the Vortex, have your friend try to get on it, it's VERY unstable. Last time I tried it, I was bouncing off the ground, hitting people, flying into cars, hitting buildings etc. It ended when a car hit me and made the Vortex explode :(
5. Activate the "Riot" cheat and "Pedestrians have guns" cheats and run for your life. I absolutely love chaos :)
6. Bike jump onto the tallest building in the first city. It's the one with the parachute on top of it. You have to activate the 'Bike jumps higher" cheat to do this obviously. I know you can walk in the door and get to the top but it's more fun this way, plus when you're on the top, you can jump off with your bike. You can get a bike from the area by the police station in the first city that has all the ramps.
As soon as you get the bike, go out the opening to your right, and go down the street then turn right at the intersection. There will be a building down the street. Jump on it. Then turn left and jump onto the other building. Turn left again and you'll see a long building. Jump on it. There's a rocket launcher here btw. To your right, there's another building that has a low platform, between two higher level platforms. Jump on the low one. You can go for either side but I go for the left one. Either way, back up all the way to the opposite side of where you're going to jump then pedal softly enough to get you moving, then jump. Once you're on, back up the ledge, then pedal forward a bit, and jump again. You should be on a second ledge, do the same thing .After you reach the top, you should notice the tallest building, with one next to it, jump on the one next to it then go for the tallest building. The last jump is hard, wait til you're almost off the edge before letting go of your charged jump. After that, have fun :)