I remember a Rig Rundown video with Nita Strauss where she said she uses her signature ibanez exactly as they are in the shops.
Matt Freeman of Rancid had a signature Squier P bass but he's only ever played his Fender live.
Doyle from Misfits (the guitarist) was asked about his signature guitar in an interview. To say he was not complimentary would be an understatement, he said no one should buy it because its all wrong.