Probably no one remembers OVAL pizza the all time worst, cheapest pizza that, back in my day, you could pickup for $4.99 for an extra large. It would leave a distinctive long-lasting wet cardboard smell in the elevator for hours. The cheese was so thick and plastic-y that I once inadvertently buried an Oval pizza box under newspapers and laundry - only to find it again two weeks later, microwave it and it tasted like new (which, to be honest, wasn't good anyway)! The plastic cheese layer was impervious even to salmonella!
No respect for Donato's pizza? The founder's favorite with banana peppers ranks very high on my all-time list.
The late-great Flying Pizza just north of 15th gets an honorable mention - walking home from class eating a New York-style slice with meatballs ....fuhgeddaboudit.