There are so many tendon eateries now, but this still remains #1 for me. They don't skimp on the (quality) ingredients, and you also get chawanmushi and free-flow tsukemono (pickled cabbage). Kohaku came close especially with their spicy sauce, but they can be rather inconsistent.

The batter gets soggy fast but it's really meant to be eaten quickly. Moving the tempura onto the shallow bowl helps to keep the pieces remain crisp longer though.