S.L.U.G. Zombies had a couple figures that you could probably harvest for 1:18 figures. I have a couple but don't know where they are at the moment to show size comparisons. Most of them had heads that were just a bit too small to be useful though.
WWE DG Figures work great, Rey and Orton might only work on tiny, tiny bodies. Taker looks awesome on a Roadblock body.
SWG has the Halo Avatar helmets in his store, those are awesome! SWG, do you have series 2?
The WWE Rumblers, I thought I had pics saved of some of them, but I guess they were on my phone. Some of those are great, some not so much..
EDIT: Found the pics, they were ones I sent to a friend when I found them...
I think the other one was Ultimate Warrior, lol.. I didn't bother with him because of his big 80s hair-do.
McFarlane NFL blind bags, some could work, but most are too stylized.
There were some comic book packs at TRU that had Stan Lee and I forget.. one of the recent directors... sigh, anyway, VCA has the Stan Lee head in his shop. Not sure on the Director who's name I can't recall...EDIT: Joss Weadon
There are also some Disney World "Playsets" that have some heads that could be used. These are more animated in nature but there are some sets from Indiana Jones, Star Wars, Marvel, and some others that include more realistic sculpting.
I've already gotten rid of him. I didn't open it, but just from pulling the figure out of the shipping box I could tell it was no good. It's a weird size - too big for MU scale but too small for ML scale. Might work well with something McFarlane sized. So if you want Stallone to become a Walking Dead cast member, now's your chance.
I was strolling through TRU today and ran across a couple types of figures that may have some usable heads for creature and zombie type figures.
[ame="http://www.amazon.com/s/ref=nb_sb_ss_i_0_11?url=search-alias%3Dtoys-and-games&field-keywords=beyblade+warriors&sprefix=beyblade+wa%2Ctoys-and-games%2C195&rh=n%3A165793011%2Ck%3Abeyblade+warriors"]Amazon.com: beyblade warriors: Toys & Games@@AMEPARAM@@http://ecx.images-amazon.com/images/I/41fEqFM388L.@@AMEPARAM@@41fEqFM388L[/ame] Beyblade Warriors- They are a "top" fighting game. I've been waiting for those to go on clearance for a while to see how their heads would work.
I picked up 2. This one was a hawk type character. He'll need a bit of work hut its at least the right size.
They also had some 2" fighter things called Mutant Mania that came in soda type cans. They heads are separate so they wont need too much work. there are 120 different figures so I'll have to look into those a bit more to see if they have some viable heads. They were a bit on the smaller side but could work on a small body.