The closest to the grassy knoll are the Palm and the Y O Ranch steakhouse in the West End. Bob's in the Omni is also close. Stephan Pyle's is just up Ross Ave offering upscale southwestern fare. Javier's is at the north end of McKinney Ave offering Mexico City food and a great cigar bar with superior people watching.
Al Biernat's steak house on Oak Lawn has great steaks and the best chance to see someone famous.