Not too sure if it's their original idea or they "copied" from another company, but I like Panini's "Private Signings" autograph cards.
Nice design. Clean space for autographs - all on-card (so far).
Currently collecting (basketball only): SkyBox Premium Autographics (1996-97 to 1999-00),
Stadium Club Co-Signers (1997-98, 1998-99), Topps Autographs (1997-98 to 1999-00),
Panini Private Signings (2010-11 onward), HOF on-card autographs, and anything that catches my eyes.