Lets hear em! We've all got those stories of when you spent hours/days/weeks on an issue with your truck just to find out it was something stupid. I've got 2 to start us off:
Back when I had my '01 and used to take it off road occasionally, I had my windows partially open one nice afternoon driving home from work. Stop at the supermarket and discover my driverside window won't go up or down. So I leave it partially open and go into the store wondering what the hell. Drive all the way home and start taping up the open gap because it's supposed to rain cats and dogs the next day and I wouldn't have time to look into it until the weekend a few day later. So I get it all taped up and about an hour later when telling my wife about it she says "do you have a window lockout button?" Duh! I felt so stupid. hit the button and window worked fine. All that time I was thinking maybe I corroded the motor in the door after sinking my truck 6" above the door sill in a mud hole a few months earlier.
Second story: just today I had this rattle that sounded like it was coming from the passenger side. Leaned over while driving to try and hear where it was coming from. While leaning into the passenger side, it sounded like it was coming from the driver side. WTF? I spent my whole lunch hour checking my glove box, inner door panels, etc... Started thinking since I just had my windshield replaced a few days earlier that some broken pieces of glass ended up inside my dash and started cursing the installers. Then it hit me - my sunglasses in the overhead console were put in akwardly the last time I put them away. That was it. The rattle was coming from my sunglasses in the overhead console. Duh! Re-positioned them and no more rattle.