NifSkope
From GECK
NifSkope is a utility for viewing and editing .NIF, .KF, .PSA and .RDT files.
.NIF files are typically models, but can also contain extra information, such as animation or collision, depending on what is needed. .KF files are animations for actors and weapons. They contain compiled animation data as well as time stamped sound cues. .PSA files are poses for actors to take on death. They contain placements for bones that are assigned to an actor's ragdoll on death. .RDT files are a way to redefine an actor's ragdoll data based on their current armor. Functionality is broken in Fallout 3 and New Vegas, they should not be used until a fix is made.
Nifskope x64 for general use, includes the shaders.
Nifskope x86 Only for updating MOPP.
