I Use:

Susie Plugin 32x:
A Handy software made by takechin that is used to rip sprites from many games, I Use it to rip the sprites from The Queen of Heart '99, Eternal Fighter ZERO
& Touhou Suimusou
(Immaterial & missing power) (NOTE: Both plugins made by sue445, There is another QoH '99 plugin i use from Hiroshi INOUE though).

KFX/KFA Offset viewer:
A Software made by yotoman that is used to view sprites' offset from KFX/KFA characters, may not be useful because it only views sprites & you cannot save
them (Although you can capture them with AnimGet).

Higebu:
Made by the same author of the "KFX/KFA Offset viewer", this time it allows you to view animation frames/hitboxes of KFX/KFA chars.

AnimGet:
A Tool made by Michael Meene that allows you to capture animation frames for any game (I Use it to capture frames from both EFZ & QoH '99), I Also use it
to capture KFX/KFA character sprites while viewing the sprites with KFX/KFA Offset viewer.

GIMP:
Made by The GIMP Development Team, A really good freeware tool similar to photoshop i use to resize character portrait images to 120x140.

Mugen CNS Checker:
I Use it for debug purpose (Don't even know what is this actually but i never used but i will use it for the first time).

Training (char):
I Use it for debug purpose too, it's a KFM edit that is more of a utility than a char (Allows debugging of head/midsection positions & attack distance too),
mostly used when it comes for character feedback.

Fighter Factory Studio:
I Use it for sprite addition purpose (QoH '99, EFZ & Touhou Suimusou only).

Fighter Factory Ultimate:
I Use it for sprite (V.G. Custom & KFA Only), animation, sound addition, programming, palette & etc misc stuff.

Official MUGEN Documentations:
Handful documentations with all complete list of things to read in order to make a mugen chaar.

And you?