Most would certainly be Les Mis. I had about five or six costumes, but I was changing them all them.
And though I didn't have a lot of costumes, How to Succeed was the most frustrating experience I've ever had with a costume. My window-washer jumpsuit was a velcro tear-away, and it was not only a pain in the ass to put on, but I was constantly worried it wouldn't come off during the performance. Fortunately, I actually loved my costumes in that show.
I am a firm believer in serendipity- all the random pieces coming together in one wonderful moment, when suddenly you see what their purpose was all along.