Team 708 has really stepped up their on-the-field game over the past few years, and is the best non-winner in MAR that I can think of (now that 1089 has a division banner).
https://www.thebluealliance.com/team/708/history
1x Regional finals (2009)
2x District event finals (2012, 2016)
1x Sub-division finals (2016)
2x District Chairman's Awards (2016, 2016)
1x MAR Championship Chairman's Award (2015)
FeelsBadMan
3974 and 4954 are some (relatively) younger MAR teams that are still looking for their first wins.