Here's a few I've done:
I've got a bunch of different exotic skins on hand - stingray, ostrich, elephant, hippo, zebra, giraffe, alligator, python, shark. I've never had really any problem sewing through any of it. Again - as Shorts said it's the equipment used that makes the difference.
I use only genuine skins - none of the embossed. The silver on the tan colored cowboy holster is real silver. The spots on the one just above is the generic type. (That's beaver tail on the band.)
Excellent work K Man! Very nice! Any more examples?