They use custom Amfisound guitars, Antti has a custom Routa called the "Atrain", if I recall correctly he has a Dimebucker in the bridge position and a Seymour Duncan Jazz in the neck position, it's got a maple neck and alder body in neck-thru design, ebony fretboard with 24 frets. I don't recall ever being able to find much on Pekka's guitar though.
Amp wise, they used Line 6 AX212s for the first 3 albums and used Peavey JSXs through Laney cabs on The Black Waltz. Not sure what they've used since then but I think I read something about them switching to Krank amps, no idea what model though.