5 E. 51st Street btw 5th and Madison
I've gone on about this place for the past ten years, since I first started eating here when I worked at 666 Fifth Avenue. It's always been my standby for meeting friends for a midtown lunch or to take a short sit-down respite when up near St Patrick's.
Their slogan is "A burger is a burger is a burger. Ours is PRIME!". Gotta love a diner with it's own slogan. They have individual tables where the top swings out, like a grade school desk, decor that hasn't changed since the early 60s, homemade pie, decent burgers (make sure you ask for any extras beyond meat, bun and cheese) PLUS grilled cheese and tomato soup every day of the year. They also were given a James Beard Award in 2004 for being an "American Classic."
Gene Shalit once harassed me during lunch; I sat next to a guy with a HUGE Yankees 1996 World Series ring (never did find out who he was); and a waiter in the white jacket-and-tie staff uniform once sang the whole of "Wichita Lineman" to me while I was eating. Home of the nicest staff ever, most of whom have been there at least for the past 10 years, they always remember me and say "Where have you been? Don't you work nearby anymore?" when I don't show up for awhile. A truly only-in-NYC type of vibe, it makes me happy to walk through the doors and sit at the huge counter.