Getting a specific Energy Sphere in Kirby's Return to Dream Land. It was in Dangerous Dinner where Kirby has to push specific switches while leaving other switches untouched to guide a Key Dee to safety. I kept either pushing the wrong switches or pushed them at the wrong times. I got it eventually though.
Upon getting 100 coins in "Disney Crossy Road", I randomly unlocked Rapunzel, who I've got a major crush on. To celebrate, I wanted to snapshot it with my iPod Touch by holding the power and home buttons while waiting for her model to rotate to face me...unfortunately, I forgot that holding both those buttons down for a long time actually force-shutdowns the device...and when I started the game up, she got re-locked, and I instead unlocked Gene from "Wreck-It Ralph". I was like "Forget it" and bought Rapunzel for 99 cents.
I was doing an awesome job in Path of Radiance, killing everything in my path. The last bad guy was left standing when all of a sudden my units scattered to the four corners of the Earth and I was left with flipping Ike who couldn't kill an ant at this point. So, after thirty minutes of pure genius, I had to restart ALL over again. Gack. Probably my fault but whatever!!