Finishing the GTA V on 100% requires spending a lot of time with the game. But, luckily, from the technical point of view, it's not a 100% for real. Your level of completion may be checked in statistics in the main menu.
Here is a full list of required things:
- Finish all 69 missions. Those are storyline missions, but also secondary ones like Franklin killing for Lester.
- Finish 20 out of 58 Strangers and Freaks missions. They are marked with the question mark.
- Finish 14 out of 57 Random Events. While wandering around, in some moment a mini map starts flashing white and then you see a nearby blue dot. When you get close to it, an event begins. The most often is to be a robbery or somebody looking a lift.
- Finish 42 out of 59 available Hobby and Pasttimes. There are, for example, races, golf, tennis, shooting range, flight school, yoga and hunting. You have to perform all activities of the particular type, it means finish all available street races (5), all see races (4), triathlons (3) etc. In case of activities for which you obtain medals (shooting range, flight school), you just need a bronze one for each task. To complete a Strip Club, you have to buy a private dance. To complete tennis, golf and dart, you have to win one match.
- Rob the shop (enter the shop and aim at the cashier).
- Buy a car through the Internet.
- Buy five generating income properties.
- Perform 25 out of 50 Stunt Jumps.
- Perform 8 out of 15 Knife Flights (fly horizontally between buildings in proper places. The best way is to use an army jet, which can be stolen in Fort Zancudo).
- Perform 25 Under The Bridge (fly 25 times under the bridge).
- Buy a hooker.
- Finish Booty Call. Minigame in Strip Club, in which you have to touch a stripper when you're not seen. When the bar fills up, you may suggest her going home with you. But be careful, as not every dance agrees and then you have to try with another one.
- Watch a movie in the cinema.
- Take Chop for a walk and play retrieve.
- Collect 50 Spaceship Parts.
- Collect 50 Letter Scraps.
- Go to the bar, watch a movie in the cinema, visit a Strip Club, play darts with two main characters. Choose a number and then an option to Hang out.
Getting 100% completion rewards you with an achievement. What is more, a spaceship appears high over the Fort Zancudo. You can get close to it, but it's defended by some kind of a force field and each trial of takeover kills you.