Powershell function to start GVim, making use of Vim's server features.

Start-Vim.ps1

function Start-Vim {
  if (!$global:VimServerName) {
    $global:VimServerName = 'GVIM'
  }
  if ($args) {
    gvim.exe --servername $global:VimServerName --remote-silent $args
  } else {
    $servers = (vim.exe --noplugin -u NORC --serverlist) | ? { $_ -eq $global:VimServerName }
    if ($servers) {
      vim.exe --noplugin -u NORC -c "call remote_foreground('$global:VimServerName')" -c 'quit'
    } else {
      gvim.exe --servername $global:VimServerName
    }
  }
}

This allows you to keep using the same instance of GVim from the command line. If you call it with no arguments it will either start a new instance of GVim or bring a running instance to the foreground.

Make sure to set a more convenient alias, e.g. Set-Alias vi Start-Vim.