With the pre-GUP albums, "least favorite" was an apt term. Not so much anymore. Of the remaining songs, the one I dislike most is Scars, but I voted for Stupidconductor.
This is a very bi-polar album. There were a lot of not very good songs on GUP through HYF, but Presto was the first Rush album that featured a song that I found embarrassingly bad (HOF). On the other hand, it also features what I think is Rush's most underrated song and possibly my favorite post-Signals song.