If you have the VMware-VIM (vCenter Server) ISO image, the client is included on the disk. Mount the ISO on your Windows system. Run autorun.exe .
VMware does not allow hotlinking, but the general pattern is: vsphere client 6.0 download link
To summarize, there is no single public, anonymous "download now" button for vSphere Client 6.0. However, using the official methods above, you can securely obtain the installer. If you have the VMware-VIM (vCenter Server) ISO