I have a very varied collection.. I started on High Grades, but now i mostly pick up 25cm X-Plus, SHMA, and the occasional M1 or Marmit MH.. not really a completionist on any account except when it comes to Showa Meganurons.. i will buy any variant that i don't already have. So here is my current Meganuron collection:
Up top is the very large (almost 2 feet long) X-Plus release from 1998, the four identical sculpts are Toygraph releases.. I'm always on the lookout for more variants, there at least 2 or 3 others that i have seen pictures of that i dont have, and i am strongly considering getting a paint job on the unpainted red figure. In the middle is a Marmit Vinyl Paradise (according to ClubTokyo there is translucent blue variant as well).. the front two little guys are both Iwakura releases and the larger one to the right is the Ricboy exclusive that came with the 25cm X-Plus 1956 Rodan.. Lastly is the Jun Planning bottle cap, which is a surprisingly good sculpt... I also have two variants of the Iwakura Rodan hatchling that features some tiny meganurons, but I didn't think about those when i organized the picture.
So i don't really know of that many others aside from a few kits, but there is a CAST figure that I have lost a couple YAJ auctions trying to get.. but the quest continues.