My first playthrough of Final Fantasy IX. I was almost through the ruins of the Burmecian capitol, and had already encountered more than enough of the damn things to know that the place had a SERIOUS Mimic problem. I was literally just one step from the exit to the next area and wanted nothing more that to forever turn my back on that Mimic- (and random encounter-) infested dump... but there was just one more chest. At the end of a narrow walkway. Just a few paces away.
I couldn't do it. I couldn't leave that chest alone. (Hey, there could be MONEY in there!) So I went those few extra steps. And guess what: I ran into a random encounter EVERY SINGLE STEP of the way over to that chest. I must have hit almost as many random encounters on that walkway as I had on my way through the ENTIRE rest of the area. By the time I finally made it to that chest, I was clean out of magic and down to my last handful of healing potions.
As for what happened when I opened the chest... Do I even need to say it?
Also have to mention Dragon Quest VIII. I was on my way to Trodain Castle, almost clean out of magic and healing items, and spotted two things in the distance. One of them was a chest. The other was a Mimic. The Mimic was one of those monsters you can capture for use in that Monster Arena sidequest, so it was happily blowing its cover by dancing merrily around near the chest. Well, I could certainly sneak up to the chest without picking a fight with the Mimic. I thought. I was wrong. However, I did manage to defeat the creature, though it cost me my last healing potion and most of the party's health.
And now, the funny part. The other chest? Yup, THAT was a Mimic TOO!