@Brian Boru started this in the weekly thread, but it seemed fun enough to me to merit its own thread (but, then again, I think letting everyone know I had muffins for breakfast merits it's own thread). Mods, no hard feelings here if you merge this back to the weekly thread).
20: Shoot all the red barrels, even if no enemies are around.
19: Try to climb impossible mountains to get to your waypoint rather than to go around as the game wants.
18: Smash buttons during title screens, warnings, etc. trying to make them go away.
17: Spin your character/camera while NPCs are talking.
16: Kick enemies off cliffs/ledges
15: Hoard everything (inventory)
14: Go the opposite direction you know the game wants you to go.
13: Shooting lights to see if they go out.
12: If there's water, you at least try to jump in and swim.
11: If there's lava, you stand in it.
10: Obsessively clear out dungeons, often rechecking areas you know you've been.
9: Obsessive closet checking.
8: Hoarding ammo.
7: You frequently refuse to heal, or at least delay that significantly, often leading to death
6: Focus on the minimap instead of the game.
5: Unnecessary grinding
4: Mash buttons to make your character go faster
3: Refuse to give up your favorite gear/equipment even after it may be outdated
2: Doing all side missions and quests before doing the story
1: Falling asleep during play