Random fact of the day: panino is the Italian word for sandwich. Panini is the plural form for sandwich.
Therefore "panini sandwiches" means "sandwiches sandwiches."
Why does this bother me? (I'm sure this happens with other foreign foods, but I only have a working understanding of spanish and italian.)
It's just stupid.
The Italian word for pizza is "pizza," its plural is pizze. You don't see Domino's advertising for "Pizzes," do you? No, because pizze was properly anglicized into "pizzas." If you want to anglicize panini, it should be "paninos."
Finally, no one should ever say "panin(o/i) sandwiches"- that's like saying "carne asada roasted meat."