PiP for Mac - Always on top window preview similar to the popular windows only OnTopReplica
PinWin - Download PinWin - Pin On Top for free. Pin any window to be always on top of the screen. PinWin is a minimal Windows system tray application that allows you to pin any windows to the top of the screen with one click.
Pennywise - Cross-platform application to open any website or media in a floating window
DeskPins - DeskPins can be used to make any application topmost, that is, to keep it above all other windows.
Afloat - Create beautiful invoices in 3 clicks, without mistakes
Stay On Top - Set a window to stay on top with this single-function but handy application.