Go to MacAlpine's! Now.
Seriously. I love this place. I live near 7th Street and try to support the local businesses as much as possible. And places like this make it incredibly easy.
They try and keep it as retro/vintage/original as possible. The ice cream and just desserts in general are fantastic. The food has always been pretty good too. The servers are always dressed in vintage-esque attire. Everytime I've been there the crowd has always been a pretty good mix.
Even if you're not in the mood for a meal, I would recommend stopping by, cruising the vintage furniture shop attached, and grabbing an old-fashioned soda. Amazing.