I'm a big fan of kitbashing. It's fun to take two (or more) disparate models and merging them into something all it's own.
My most recent conversion is a Tau Ethereal that cost me all of $8.09 (not including the bits I already owned). It's not quite finished, but it's really close. It's taller than your average Fire Warrior by half a head, but I'm good with that (IIRC, Ethereals are closer to Water Caste in stature, so a little taller anyways). Up to this point all I've done it carved away plastic to make it fit into place. The greenstuff will come further down the road.
The majority of the body is the Celestial wizard from the Empire's Celestial Hurricanum model. I modified the staff a bit by adding a topper from the Empire Wizard box (I also removed some of the fancy gilding & details to make it appear more sci-fi).
I cut away the wizard chest and replaced it with a standard Fire Warrior chest bit. To make it fit properly I had to cut away part of it's back, and trim off the belt. The head is one of the three new bits from the Pathfinder box set.
There are a few more small things to do before it's finished.
1. Carve the feet into hooves
2. Greenstuff the cloth to fit seamlessly with the chest armor
3. Greenstuff the belt buckle to be the symbol for the Tau Empire
4. Paint (after I'm done with my current commission)
Hope you like this, and that it gives you a few ideas for your own conversions.