I've seen some pretty imaginative conversions using the humble Kroot. Their role of mercenaries in the 40k universe make them an ideal candidate for such work.
In my case I needed an Acolyte for my Ordos Xenos army. I happened to have a large bag of Kroot lying around that I picked up for a dollar at the local gaming store's annual Gamer's Garage Sale. I added several bits from my guard and a spare bolter. The carapace armor on his torso, and his knee pads were sculpted using pro-create. I also used pro-create to sculpt his had wrapped around the front of the bolter. I used micro beads for the snaps on his shoulder straps and polystyrene rod for the bolter shells on his lapel.
I thought that blending the bolter with the Kroot rifle would be a little more in keeping with the theme. Once everything had been assembled as shown above I thought it needed a few more tweaks. I removed the stock scope, added a couple of Picatinny rails and a scope from polystyrene. The sling is greenstuff.
After the rifle was complete I new I had to fix that head of his. I trimmed off his quills, drilled holes into the top and replaced the quills with ones made of polystyrene rod sharpened to a point.
Pictures of the finished model coming soon!