Candy. We’ve got Snickers, Riesen, Toblerone, M&M’s, Twix, Skittles, Hershey’s. If your favorite is not on the list you may want to bring a large supply.
I’ve yet to see Instant mashed potatoes, but I heard that you can get it in Costco in Taipei. Last time to the States I brought back a 6 month supply.
Most other “essentials” you can get here in special stores, but it may require a special trip if you don’t live near one. I have to make pilgrimages (just about 1.5 hours) to Jason’s Market in Taipei for some things— Miracle Whip, Macaraoni & Cheese, Hamburger Helper for example.
The local grocery stores aren’t all that bad, though, and it’s only the special item that you can’t live without that makes you long for home.
As someone else asked, where do you live and what do you ike?