I like the 50/1.8 A1s semi-pancake for a particular reason. It's really a second-string design, but one stop down is fabulously sharp, is compact, and was inexpensive enough that I can travel with it without getting paranoid. My 55/2.8 is a better optic with better build. But I seldom shoot 35mm except for rainy days or brisk walks when I don't want to have to clean my big cameras afterwards.
And I don't generally use "normal" focal lengths. So a semi-pancake fits nicely into a little nook in the bag below the 85/1.4 I mostly use.