Blacktron mech built based on a round container from the LEGO X-Pod series of sets.

The series consisted of small sets produced between 2004 and 2007. The common feature of those was that container appearing in various color combinations.

Edit:
I got 2nd place with this MOC in the Colour it Blacktron Contest (VII) in the category "Built a Blacktron MOC that isn't an obvious remake of a set"