So this is all-time obviously not current. You also seem to be doing narrative, bad blood, entertainment based rivalries. So I'd say:
FL = Cejudo-Dillashaw. Or Mighty Mouse-Cejudo. One being a one-off but champ vs champ with some bad blood.
FW = Aldo-Conor for WWE hype sure. I'd agree. But Holloway-Volk is a pretty good one considering Max probably won the 2nd fight. Faber vs Aldo was the original.
LW = I mean, again we're going off recency bias and a one off fight. Penn-Edgar, Bendo-Edgar, Maynard-Edgar are all great rivalries. Khabib Conor is one fight, but sure in terms of popularity contest and bad blood, fair.
WW = Hughes-GSP? or recently Usman-Covington is a candidate but pales in comparison magnitude wise.
MW = Sure. Weidman-Silva is up there too. Franklin-Silva, Rockhold-Bisping, Whittaker-Romero-Adesanya, others for sure. Costa-Adensanya if the criteria is bad blood/story.
LHW = Good one, Jones-Cormier obviously, top tier talent. But it kind of flies in the face of your trend. Tito-Shamrock takes the cake there easily if it's narrative. Liddell-Tito-Couture as well.
HW = Stipe-DC has to be up there, elite tier trilogy. Has that ever happened at HW before? Cain JDS had one too, but it was 1-2 not 1-1-1. Cain-JDS and Stipe-DC have to be up there. Fedor-Big Nog is definitely up there. Carwin-Lesnar off hype and excitement was a big one off, not deserving to be in 1st though at all.