Actually, a milkshake is called a cabinet in some other parts of New England, as well. In RI it is frequently called a frappe. I’m not sure if the rest of the country has what is called a milkshake in New England. It’s milk and syrup whipped up, without the ice cream.
Del’s frozen lemonade is a good one. I’ve never had anything quite like it anywhere else.
Coffee milk is another thing that’s almost unique to RI. It’s made with coffee syrup from either Autocrat or Eclipse.
Another is the Awful Awful, which is sort of an ice milk shake made at Newport Creamery shops in RI. Friendly’s has a cheap knockoff they call a Fribble.
Don’t overlook Manhattan Special, the delicious expresso coffee soda from NYC.