This hole-in-the-wall institution,bustling day and night, is the place to go for speedy, hot, supercheap, and delicious Middle Eastern food. Tahini-topped pitas are packed with fresh, green-on-the-inside falafel balls. Be warned: the hot sauce is incendiary. The small space has a few tables, but this is food you can easily eat on the go. Best of all, it's open every night until at least 4 am. The original Mamoun's is still on MacDougal Street, near Washington Square Park in Greenwich Village.