Every Playbill I own is prized. Off the top of my head:
Spamalot (my first B/way musical for years) - signed by David Hyde Pierce, Hank Azaria, Steve Rosen, Christopher Sieber, Michael McGrath, John Bolton, plus more playbills afterwards signed by other cast members.
Curtains - signed by David Hyde Pierce, Debra Monk, Karen Ziemba, Jason Danieley, Noah Racey, Edward Hibbert, Megan Sikora, Jill Paice, Michael X Martin, John Bolton, Michael McCormack and Ernie Sabella
Prelude To A Kiss - signed by Alan Tudyk and John Mahoney.
Chicago - signed by Bebe Neuwirth
Drowsy Chaperone - signed by Bob Martin
November - signed by Nathan Lane, Laurie Metcalfe and Dylan Baker
Dirty Rotten Scoundrels - signed by Jonathan Pryce and Greg Jbara
Xanadu - signed by Kerry Butler, Cheyenne Jackson, Mary Testa, Tony Roberts
I have some other playbills / programmes from Broadway & the West End, but I'm not an avid 'collector'. I prefer to get autographs from performers who I've found particulalrly entertaining. Hopefully that will include Roger Bart, Christopher Fitzgerald, Sutton Foster and Megan Mulally next time I'm in New York.
Seen some shows in my time....