This is going to be a thread full of people's favorite games, rather than the influential ones.
Looking through the thread I'm actually surprised how little of that there is.
I think the original list and
@Snarf Zagyg's one are pretty good.
I'd personally add:
Dogs In The Vineyard - Obviously hugely influential, surprised it's not on either big list and fits your "under the radar" descriptor too.
Feng Shui - I think that Feng Shui really kind of fired the starting gun for lot of modern design, and particularly for RPGs that tried to use rules built specifically to emulate genre/tone, rather than rules bolted on to existing systems, which usually attempted solely to evoke specific genre tropes, without actually attempting to emulate the genre in a wider sense (the latter was common with GURPS supplements, for example). I think it's a weaker pick than DotV though.
I'd remove
Savage Worlds because whilst it is a good game, I can't think of anything or anyone who has been influenced by anything its doing, design-wise. I'd also personally remove
Sorcerer because whilst it is an interesting and weird game, I'm not actually aware of it having any influence, but this could be ignorance on my part, so I'd definitely be open to hearing what influence it did have.
The rest seem fairly solid.