There are plenty of possibilities. Personally, I love roses the most. If you take a good care of them, they bloom often, and they always look gorgeous.
As for tulips, it makes me really sad that they don't last all summer They're so pretty! I already miss them.
I like geraniums myself. As long as you clip the old blooms off they will bloom all summer.
I like the smell of the foliage as well: it smells just like where I grew up. Unfortunately they are a TENDER perennial, and so where I live they will die during the winter. Zone 5 is too cold for them!