So far the most popular franchise with this is Transformers, but most of their media is mediocre at best. There are some exceptions like a few of the comics and some of the series which are really good, but overall as a franchise they are lacking unfortunately. I really love the trope though.
The other franchise with this would be Bionicle but I can't say I know much about it.
There are plenty of mechas out there, but they don't tick all the boxes for this trope. Most are either non sentient or require a human pilot to be active. And those which are sentient and autonomous are rarely fighters.
So if you know of any - please let me know. Thanks.
Evangelion has been on my list for too long, I just don't have time for anything in my life. So does each one have their own distinct personality, motivations etc? Are they actually characters or are they more like props?