On my models, I use Custom Content by other creators. I mostly use skintones by LadyFrontbum, Ephemera,  Kurasoberina and LemonLeaf.

I also use my own skintone blend on some of my models.

I use lots of custom hairs, some of my favorite meshes and retextures come from Cazy, Newsea, kittyklan, #aWT, Kijiko, Anubis, Lotus, Metalmoose, Beaverhausenx and a bunch of others... I can't possibly name all!

I use and abuse Awesims' wonderful screenshot backdrop!
I couldn't imagine my sims without the 3D eyelashes from S-Club.

I use a lot of different poses, I couldn't possibly begin to name them all so a big thank you to all pose creators for your great poses!

I use Milkshape (with WesHowe's awesome plugins), Blender (wih Cmomoney's plugins) and Balancer Lite for meshing. Cmar's Meshing Toolkit for adding morphs and bones.
I also use Inge and Peter's S3PE, S3OC, Texture Tweaker, Delphy's Custard and Dashboard Tools for Sims 3 CC. Some old creations were made with CTU. Some patterns were made with Delphy's Pattern Packager.
For Sims 4 CC, I use S4PE, Sims 4 Studio and TSR Workshop.
For texture and image editing, I use Adobe Photoshop.

And last but not least, a special mention of the awesome Pose Player by Cmomoney.

Thanks to all developers for their great tools!