My first was AnimeDollM3. (I followed the tutorial). I have done many more hybrids (M3Freak, SPA3, V3M3, V3MM3, M3H3D3Freak, SPV3, A3V3, M3Luke, M3Matt, M3Apollo, M3Baby3, GremlinOni, M3V3, etc)  but most of them were lost when my machine died. I don't have pictures of them either. The H3/M3 image I was able to recover from the Poser Pros' forum.  The wildest hybrid I attempted was making Mill Dog a Bi-ped that could wear M3 clothes. After awhile it became obvious that it wouldn't work, there aren't enough polygons to work with, not to mention, I would have change MilDog's groups so he would loose all his morphs. And he posed like crap too. Oh well. It was fun experiment.

Some of the tools I use are:

Blacksmith3D -
This is my main tool now. H3M3 was made with Blacksmith. All my custom head morphs are done in Blacksmith now too. Easy way to fix texture seams too.

Wardrobe Wizard -
Yep. I use good old WW's "smooth" to fix head and neck seams. Works like a charm.

Poser Tool Box -
Good for morph target obj export/import and face putty-ing a basic face shape with super smooth magnets.

UMT (Universal Morph Transfer) -
I used UMT to convert and make INJs of custom heads between group 1 and group 2 Daz Mil3 figures. Older Frankenstiens like taking a custom M3 head and reverse aging to Mill Baby were done this way.

Magnets, Obj exports, Morph Targets
Using Poser tools to take one head and pop it on another. Used for Gremlin/Oni. Now Oni can wear Wardrobe Wizard converted clothes for Gremlin. ^^

ShapeShifter -
Kam's easy python script  to swap Mil3 head.

Other hybrids on my list of  To Do's are:
Koji-M3, Miki-M3.  A3H3-MilBaby.
Koji has a great face and expresisons so I want try to popping him onto M3's body. But I may not be able to get a Bishie look of him, so I was wondering if a masculinized Miki would work. And of course making a cute Chibi figure with Mil Baby would be cool. ^^

bB