Quite a few:
STUFF HAPPENS--terribly glib, poorly written and acted, and offered nothing new about the subject it was trying to discuss.
MARY POPPINS--too many kids around (my friend and I specifically chose to go to a midweek evening performance because we thought we would avoid this; not so, apparently) and it just wasn't fun, which is the whole purpose of the show.
ASYLUM--a musical at the York about Mary Todd Lincoln. When the chorus of three came out and repeated the lyrics "Crazy Mary/Mary's Crazy" for five minutes straight, I knew I had to flee.
MR. FABULOUS--another show at the York, this time a developmental reading about a Liberace-like closeted pop star and his young lover. There were 10 people in the audience when the show started and maybe 3 left after the interval.
LES MISERABLES--the revival. Gemignani and Lewis were miscast, Salonga wasn't even trying, and the Marius and Cosette were basically just trying to see who could sing higher. The tour production is mind-numbingly awful. I couldn't wait to get out.
DI YAM GAZLONIM--this show billed itself as "The Pirates of Penzance in Yiddish". Not so. Basically, a Yiddish comic writer kept the music and rewrote the show with a bunch of unfunny schtick ("When Frederic was a little lad..." became "When Fyvush was a boy a shul...", and so on).
There have been others, but these are the most recent.
"You travel alone because other people are only there to remind you how much that hook hurts that we all bit down on. Wait for that one day we can bite free and get back out there in space where we belong, sail back over water, over skies, into space, the hook finally out of our mouths and we wander back out there in space spawning to other planets never to return hurrah to earth and we'll look back and can't even see these lives here anymore. Only the taste of blood to remind us we ever existed. The earth is small. We're gone. We're dead. We're safe."
-John Guare, Landscape of the Body