Thanks for the compliments guys! I like that everyone has their own favorite.
Alright, parts breakdown:
Blood Slaughterer (not the most elegant name)
Torso/hips:
DE Talos with tank-hatch ring for mount.
Head: Defiler Mask
Tentacle arms: Maulerfiend lasher tendrils
There's also Sentinel exausts on the back, and a maulerfiend melta-cutter armour thing on the front.
Legs: Robogear Spider (robogear is cheap and pretty crappy, but they do have a few really cool bits, like various mech legs)
Contemptor
Torso: Ork Dred, with front plate from WFB Chaos Chariot.
Head: nother Defiler mask with horns from some WFB kit. Gorget bits are from Dragon Ogres I think.
Forgefiend hades autocannon (butcher cannon)
Legs: Mauler/Forgefiend with Sentinel feet
Punchy arm:
GK Dreadknight arm with Maulerfiend hand and shoulder pieces.
Maulerfiend Bull:
Front legs: Sentinel legs mounted backwards
Head: WFB Beastman Ghorgon
Tail:
DE Talos with Ogre club on the tip.
The photo perspective is sorta wacky and looks like he has a giant head, but it's actually fairly well proportioned.
It's been in other threads, but here's my one finished walker of the bunch, their big, slow, hic cousin.