The Rock Shox shock pump with analog gauge is suitable for all spring elements with car valve. The somewhat larger version with about 20.6Bar (300psi) is sufficient for most suspension forks and dampers.
For some special dampers like the Pull Shock dampers from Scott and Fox / Cannondale you need more pressure, then you need the variant with about 41.3Bar (600psi) maximum pressure. This variant is also necessary for filling the so-called nitrogen chamber in Rock Shox dampers, but you must also buy the matching valve adapter.