Alessa Gillespie - Chose to give "birth" to the chief deity of Silent Hill. I place the word birth in quotation marks, because the whole birth of God appears to be more of a transformation. Alessa herself will take on the appearance and personality of the woman in white. In a nutshell, she'll look just as she does now, only surrounding by light, and wearing a white one piece dress.
Personality wise, Alessa/Incubator will be wanting to save everyone. And of course, save really means "destroy everything with fire." Don't worry, she's not going to succeed. Also, she'll claim that her name is Alizer.
Info: The Halo of the Sun has four names written in Runic. Dahlia, Alessa, Alizer, and Incubus. There's been all manner of theories about the identity of Alizer, and the one I subscribe to is the one that states that Alizer is the name of the entity that Alessa transforms into at the end of SH1.
Flauros/Melekiel - Didn't follow Mephistophelis/Letemael out of Heaven, and remained as one of God's holy angels. On this day, Flauros will go by the name "Melekiel" will actually be genuinely nice, and will speak the truth.
Raziel - Never wrote the Sefer Raziel, and as a result never grew as the angel of secrets or mysteries. On this day, Raziel will have no interest in learning, and will be watching all manner of mindless entertainment.
Mark - Never became a 'Christian' and is instead an atheist. Due to this, Mark has none of his abilities. (His power was awoken when he converted to Christianity. No conversion, no awakening, no power.) Will still act like a jackass, but not too badly.