Packages with the pci use flag

app-emulation / vice : Versatile Commodore Emulator

Enable PCI device discovery using sys-apps/pciutils

app-misc / ddccontrol : Control monitor parameters, like brightness, contrast, RGB color levels via DDC

enable direct PCI memory access (the setuid ddcpci util)

net-analyzer / net-snmp : Software for generating and retrieving SNMP data

Use libpci (from sys-apps/pciutils) to look up network interface description. This feature is only available on Linux.

sys-apps / cpu-x : A Free software that gathers information on CPU, motherboard and more

Use the sys-apps/pciutils library for PCI info

sys-apps / hwloc : Displays the hardware topology in convenient formats

Enable PCI device discovery using libpci