MMs and UMMs that aren't JAMMBO's

Some firms that I think fit your criteria:

Differentiated Investment Strategy

• KPS - deep value investing focused on turnaround buyouts (buying distressed or stressed companies and doing some pretty heavy operational work), also would consider them industry-differentiated (the people there are very smart on the industrials space)
• H.I.G. - probably the largest industry-generalist value investor in the MM space (focused on buying underperforming companies or carving out an unloved segment of a business for cheap and helping improve / change the direction of the asset); another fund that would fall into this category would be One Rock
• Centerbridge - value investing in both traditional buyouts and credit (special situations), one of the few places where you can get such a wide breadth of experience investing all across the capital structure

Industry Specialty

• Veritas - they've scaled so quickly it's hard to consider them even UMM anymore with the check sizes they write these days, but they're the experts in investing in government-tangential industries. Focus on A&D, government services and healthcare IT, with truly deep expertise in the space (the managing partner and a handful of others at the firm have TS clearances). A similar name in this space would be ACP
• Patient Square - HC-focused firm that's pretty new but has assembled an impressive investment team + operational team (MD/PhDs on staff)
• Arcline / Greenbriar - A&D-focused firms that pride themselves on being the subject matter experts on A&D; as a result, they've dared to bid top-dollar on assets with the spin that they can find value where no other investor can because they understand the industry so well. Time will tell if that's actually true
• Searchlight - technically generalist but they play a lot in the TMT space, specifically the telecom and telecom infrastructure space
• Tech PE is a crowded field but there are some standouts in the UMM / MM space who have sector expertise