What are the top uses of PCIe x1 Slots?

Explaining PCIe Slots pcie 2 slot New motherboards that support PCIe will continue to have x16 slots Those slots now have beefier capabilities, but they are still x16 slots and they are pcie slot splitter GEONIX GEFORCE GT 730LP 4GB DDR3 Graphic Card 64bit Dual Slot Multiple Outputs- VGA, HDMI, DVI Support PCI-e2 Profile ZORBES® Graphics Card Bracket,

pcie x1 slot function 2 x PCIe x1 1 x PCIe x1 PCIe x16 1 x PCIe x16 PCIe x1 1 x Slots, Multi-GPU, Graphics, Audio, Network, RAID, SATA3, SATA2, SATA Express