For sure the Dreamcoat one.
But I also think of the now infamous Book of Kells puzzle, IQ 1733 Mirror Image IV by Serpent, Listener 4902 Threes by Miles which just required the solver to outilne PITH, JUDO and CALF but I filled each letter with a different colour. Then there was Listener 4695 Betrayal by Nudd where I coloured my representation of Rene Magritte's painting The Treachery of Images (Ceci N'est Pas Une Pipe). And let's not foirget Listener 4662 Hungry by Android that included a deletion and then moving of Poe's Nevermore repeating Raven.
I treated all of these and many more as artisticly as I could, and having a larger grid drawn on white paper gave them an energy and vibrancy that was just not possible in the newspaper's smaller grey pages.
All that said, we'll see how my hand holds up in the future - it's yet to be tested since my op and stookie removal:-)