We actually have one of these now. I got it from Macy’s on clearance (open box) for $8 or something like that. I use it to make the sandwich triangles for school lunches as a change form regular sandwiches or as-is leftovers.
My usual fillings:
Ham and Cheese
Leftover chicken meat from chicken curry
Leftover taco meat and cheese
Peanut Butter and Jelly
My kids think it’s great – they like the toasted sandwich triangles.
My most useless cookware would be my electric crepe griddle. No idea why I thought I needed one, considering I make crepes probably once a year!