Jason, the only thing I dominate these days is the carpool line.
You could do a lot worse than giving the original 9 holes at Prairie Dunes as your answer. But what fun would that be? So I'll try and take a more balanced approach. First, a few points/disclaimers. I don't know that I (or anyone else for that matter) can say these are definitively Maxwell's best. But they are all great holes in my opinion and personal favorites. I tried to spread the wealth among courses and decided to limit myself to no more than 2 par 3s and par 5s. I have assumed the conventional wisdom that the front nine at Crystal is more MacKenzie and the back nine more Maxwell although I haven't seen anything definitive on the subject. In any event, I've limited myself to the back nine for purposes of this response. If the front nine at CD is in play, then my answers would likely change. Finally, by no means have I played all of Maxwell's courses, so I'm sure there are some great holes that I haven't seen.
Par 3s:
Prairie Dunes #2 - In my opinion, all great short holes should bring both birdie and double into play. Those were my scores on my two rounds at PD.
OKCG&CC #11 - I love this hole with the creek weaving around the green. If only the dramatic blowout bunker behind the green could be reinstated.
(Honorable Mention: Crystal Downs #14; Old Town #6)
Par 4s:
Prairie Dunes #8 - Perhaps the best Maxwell hole I've played. It has everything. Terrific land movement. Strategy on all shots, A fantastic green complex, wind plays a big role.
Crystal Downs #13 - I agree with Jason that this is a fantastic hole. You have to challenge the creek on the right side to get the best angle of approach to an incredibly severe green.
ANGC #10 - OK, so Maxwell didn't originally design the hole and the MacKenzie bunker remains an artistic marvel. But is there any doubt that Maxwell's changes made #10 into one of the great holes in golf? Plus I think at least one hole that Maxwell redesigned needs to be included on the list since that was such a large part of his work and his legacy.
Twin Hills #3 - A terrific example of how Maxwell used natural land movement to create interest on a hole. This one is virtually straight and dramatically uphill from tee to green. But the heaving terrain makes it a roller coaster ride.
Oakwood #10 - I wanted to include at least one hole from a course that very few people have heard of since, like his restoration work, small town courses in the middle of nowhere comprised such a big part of Maxwell's portfolio.
Southern Hills #18 - A ball busting finishing hole on a major championship course. Equal parts gorgeous and intimidating.
(Honorable Mention: Old Town #5; Crystal Downs #17)
Par 5s:
Old Town #17 - Great land movement. A true three shotter where a mistake on any shot can lead to a big number and ending with a double green.
(Honorable Mention: Dornick Hills #16; Prairie Dunes #17)