: ASCII text file

windows
Microsoft Windows NotePad
NotePad++

mac
TextEdit

linux
gedit

: PGP ASCII Armored File

windows
Gpg4win
Mozilla SeaMonkey
Mozilla Thunderbird
PGP Desktop
PGP Desktop Email

mac
Mozilla SeaMonkey
Mozilla Thunderbird
PGP Desktop
PGP Desktop Email

linux
GnuPG
Mozilla SeaMonkey
Mozilla Thunderbird

: LTspice Circuit Schematic File

windows
LTspice

: Autodesk ASCII Export File

windows
3ds Max
AutoCAD
Text editor

mac
Text editor