McFarlane is a good idea. I occasionally buy cheapo stuff on ebay with the idea of converting them someday (cutting them into bits is a real pain in the arse though, at least when using a hand saw). Some of the dragons (dragon series) look useful as well, as do the Warriors of zodiac (
http://spawn.com/toys/series.aspx?series=385 ) for huge chaos beasties (gemini + cancer in particular), also this one (
http://spawn.com/toys/product.aspx?product=2240 , easy enough to get him out of the cage) and the crocodile king as well. There's also a huge elephantish creature (poacher), that would work well as chaos giant.
For monsters Papo mutants, Schleich (world of history & wo fantasy), Safari Toys all have something useful.
Conan series has been mentioned already, links for pics:
http://spawn.com/toys/series.aspx?series=181 +
http://spawn.com/toys/series.aspx?series=266 , also featuring an Egyptian skeleton
Fat chaos giant ( Legend of the Bladehunters: Ogre)
http://spawn.com/toys/product.aspx?product=3493another chaos giant with an Egyptian flavour:
http://spawn.com/toys/product.aspx?product=3449This would make a decent enough female giant, with some foot surgery:
http://spawn.com/toys/product.aspx?product=2128 Another Ogre, hell of a lot of work to tear/ cut off all the ugly bits (does come with a free demon though and usually is dirt cheap on ebay:
http://spawn.com/toys/product.aspx?product=1894 )
Undead giant (aka Grendel)
http://spawn.com/toys/product.aspx?product=3356There's some more, have a look around on the spawn toys page, then trawl ebay.
the heroclix giant size x-men frost warrior/ giant is quite big, not action figure big though (and easily removed from its base):
http://heroclix.com/wp-content/uploads/2011/09/frost-warrior-ver2.jpgSafari Toys Cyclops again not an action figure and 'only' ~11cm tall:
http://safariltd.us/collection/collectionproductlist?collection_id=15&group_id=4&productid=801829