Tryall, Champions, and Preston Trails are probably his most famous courses but he also did Dallas Athletic which hosted the 64 PGA. I think Plummer wouldn't be a site favorite around here because it seems that he liked trees, a lot. I know Jeff Brauer and Lou Duran did an interesting piece on him, I think both were members at Great Southwest which I think is a very underrated Plummer design.
Jeff Blume might have some insight having just redone Texas A&M Golf Course. Plummer did a lot of fun stuff, nothing groundbreaking but enjoyable places to play. Eastern Hills in Garland is a very under the radar solid course, Hillcrest in Lubbock was the class of The Panhandle until The Rawls came along. I know our own Mike Beene is a big fan of Ridgewood in Waco. I think The Honors (used to be called Columbian) is solid and Wichita Falls CC is pretty good.
Like most architects he's done some crap but I don't know how much of that was him and how much of it was what he had to work with. Oak Grove and Pharoahs could both be nominees for worst courses ever.