One thing I can't resist is good fried fish. I'm occasionally in Allentown and it's become a tradition for me to get a "double fish" sandwich at a joint on 7th St. (on the block below Tilghman on the left side of the street). The place is sort of a combination fish market/Chinese food joint, and has Jamaican hot sauce on the shelf and Jamaican sodas in the cooler.
The fish is whiting, thin fillets expertly breaded and perfectly fried. Served on white bread or wheat, a 2-fillet sandwich is only $2.25.
Nothing fancy, but irresistible.