ZDoom

run, %comspec% /c start gzdoom.exe -file test.pk3 -height %A_ScreenHeight% -width %A_ScreenWidth% +fullscreen 1

D'oh, thanks!

Edit that was need for this AutoHotkey script:

[code]run, %comspec% /c start gzdoom.exe -file test.pk3 -height %A_ScreenHeight% -width %A_ScreenWidth% +fullscreen 1[/code]

Yes, it starts gzdoom using the same resolution as your desktop!

I normally am against workarounds but this literally already exists and is a command line option:

zdoom.exe +fullscreen 1 (launch fullscreen)
zdoom.exe +fullscreen 0 (launch windowed)

You can also set the window size this way:

zdoom.exe +fullscreen 0 +vid_defwidth 640 +vid_defheight 480 (launch windowed 640x480)

Any CVars can be set at launch this way: http://zdoom.org/wiki/Command_line_parameters

On another topic, a real, borderless windowed mode like in modern games would be nice to have for ZDoom...

EDIT: Ah I forgot one important thing; using + saves the value to the user config. Might not be desirable if the user does not want this to be persistent across sessions

-fullscreen 1/0

or -fullscreen and -window?

Which starts the game in fullscreen or windowed mode...

Borderless pseudo fullscreen would also be nice to have, -noborder 1/0?
Something akin to r_noborder 0/1 in call of duty and quake games, thanks.

If you disable window borders, and match the game resolution to your desktop, you get nice fake fullscreen!