In the case of the titan I had the idea for using a glue bottle as a plasma gun and old yarn cones to make the body and lower legs for some time. But the real breakthrough was due to my lovely wife Beth, who came across a duffle bag of toy robot parts at goodwill and snapped it up for me. Most of the parts were modular bionical parts, which work well for making the limbs of a titan. For those thinking about purchasing them however, they are hideously expensive new - you almost might as well buy a forge world titan. But Beth got me enough for several Titans for $5.
My concept was an old style warhound of the original Armorcast type. The new forgeworld style is great, but its a lot more complex in shape, and also more blocky. I wanted to capture the "swift scout titan" look and feel from the epic game. That meant a narrow body and long legs. Chaos is easier than imperial, since its easy to add "mutations" to cover the problem spots. Plus there are more bitz options. My chaos army is Thousand Suns, so the Titan would be dedicated to Tzneetch, and to me that means Egyptian in theme. The head is modeled on Anubis, the claws are meant to be Scorpian like - a god of death indeed!
The weapon arms are interchangeable, but I really like the vulcan mega bolter from a fluff perspective.
Not sure about the two little front claws - they might get removed.
Still to do -
Sculpt the winged scarab on the top armor.
Bulk out legs and joints with plasticard plates
Fill the lower legs with sand to improve stability.
Add bitz. I'm not a huge fan of the spikey look, but my other 1K sons vehicles have them, so I guess the titan will too.
Add huge cool titan banner(s). Always one of my favorite titan features.
Paint. Black, blue, and gold.