If you copy the .NET 4 version of gacutil.exe (located in C:\Program Files (x86)\Microsoft SDKs\Windows\v8.0A\bin\NETFX 4.0 Tools) to another machine/server you might come across the issue, that executing gacutil.exe just seems to do nothing.
To fix this problem, you need to copy the files gacutil.exe.config (also from C:\Program Files (x86)\Microsoft SDKs\Windows\v8.0A\bin\NETFX 4.0 Tools) and gacutlrc.dll (from the sub-folder 1033) to the same location where you have copied the gacutil.exe to.
Executing gacutil.exe should now output something like:
Microsoft (R) .NET Global Assembly Cache Utility. Version 4.0.30319.17929 Copyright (c) Microsoft Corporation. All rights reserved. Usage: Gacutil <command> [ <options> ] Commands: /i <assembly_path> [ /r <...> ] [ /f ] Installs an assembly to the global assembly cache. /il <assembly_path_list_file> [ /r <...> ] [ /f ] Installs one or more assemblies to the global assembly cache. /u <assembly_display_name> [ /r <...> ] Uninstalls an assembly from the global assembly cache. [...]