Which laser printer models have the widest Pantone color gamut? -- old or new models are acceptable.
Printerinfo.com seem to measure gamut in their printer reviews.
For example they say the HP CLJ3600n "is not meant to print photographs, and this clearly shows."
Laser printers are not really known for their photo print quality or gamut. Ink jet printers have completely dominated this arena, and currently offer far wider print gamuts than you can get from other print technologies (especially from Epson and Canon). Current ink jet printers using UltraChrome HDR or Lucia EX support wide gamut up to Adobe RGB area, and cover over 90% of the Pantone solid color set.
If you absolutely must use a laser printer, then you will probably have to deal with a pretty small gamut, I would say sRGB range at best, but likely smaller than that.