what would you say is "the" absolute best indica strain to use for crossing with sativas? white widow? which is often used to increase resin yields of strains? skunky like afghani or blue cheese? a "red hair" strain? a compact auto flowering ruderalis (lowryder) hybrid? something fruity like hashberry or california orange? a tried and true cash crop/strain like northern lights #5 which is also renowned as a good low odor strain something with a knockout narcotic stone or a similar medicinal strain? something with a euphoric buzz? something with the highest potency like herijuana? something with the hardest nugs? i hate that & like fluffy easy to break up buds much more myself. biggest nugs eg. big bud? highest indoor yields? or something else entirely? i don't know about how big it likes to grow, but maple leaf indica's broad leaf pattern & maple syrup flavor sound exotic to me. it was one of the strains used for much loved mother's finest where the hybrid scene seems dominated by afghanis & NL5 to me speed queen's coffee pheno sounds interesting too. if i'm not mistaken, it's a very compact strain too unless i'm confusing it with another royal strain. i'd lean towards strains that bring the size down as much as possible (generally compact sativa dominants like C99) without influencing the THC profile. exotic flavors are a bonus after that.
I think if you are seeking a very good pure indica strain, you will want to look at strains like Afghani #1, Tom Hill's Big Chunk, or even the Pine Tar Kush. These are proven strains which breed true and make good donors when trying to create a nice hybrid with a Sativa/Indica mix. I suggest the Big Chunk, or the Pine Tar Kush b/c they are very potent strains, produce good yields, and are true breeding pure indica strains.
Some of the strains you listed are very sativa dominant (i.e. White Widow a.k.a. Black Widow is very sativa), while others are very hybridized. Are you looking for the "Ultimate PURE Indica" to breed with, or are you just looking for a good Indica dominant variety to breed with? If you're looking for a 100% Indica strain to breed with, go with something like Deep Chunk, Hindu Kush, Afghani #1, or Pine Tar Kush as LIS pointed out. These varieties have a very solid reputation as valuable breeding material.
being a hardcore sativa fan and a wannabe breeder, i just thought it would be a fun topic for everyone to toss their two cents in. if it were me, i'd be inclined to go with euphoric hindu kush to balance sativa paranoia. i received some troublemaker freebies with the last completed dr chronic order i placed and was very impressed with their leaflet trim at least. the plants weren't particularly skunky which i prefer as skunk is "the mark of the enemy" to me. they were pretty potent even early on, and weren't really couchlocking which is the "true" enemy. i also noticed a pleasant euphoric buzz. afghani has been done to death. it would be the LAST strain i'd go with. hindu kush has rarely been used. as a go against the flow kinda guy, i like the idea of using strains no one else is using eg. burmese & malawi gold. using underrated strains is also a good way to ensure hybrid vigor with almost anything they're used to breed with, i'd go with hindu kush
I remember smoking some LUI a friend grew a few years back, and oh my goodness, that stuff was amazing, but i haven't seen seeds for it in a while, or buds for that matter, lol, but then again, i haven't been looking for it in particular
legends ultimate indica used to be THE hot topic indica a couple years ago as i said, hindu kush would be the indica i'd be most interested in having tested it in a nice hybrid and at the sativa end of the spectrum would like to use mekong haze & burmese for sativas although durban poison would be nice too if the licorice flavor could be tamed. hindu kush x kali mist would be a great 50:50 combo as both strains are euphoric & KM's restless energy combined with HK's low couchlock would be quite nice & possibly quite tasty too if you bred for KM's crushed red pepper pheno. if you add sativa dominant strains with indica profiles, i'd bet C99 goes good with everything. i bet i'll like my C99 x blueberries if one of my last 2 beans is a female. pineapple & citrus wouldn't be bad against blueberry & C99 could tame BB's size, odor & leaf curl. C99 x mekong haze would be a thing of beauty to smoke if not practical indoors. C99 x malawi gold wouldn't be shabby either i bet & C99 x burmese should be easy to grow indoors & burmese euphoria would counter C99's heart racing paranoia while the two lemony strains would have nice citrus offspring too. i've popped both spice brothers' & joey weed's c99 although never fully flowered (got as far as sexing last attempt though LOL) but noticed both strains grow very compact even compared with pure indicas. i'd consider it to be "the" pure indica that smokes like a sativa strain. everything else comparable as far as i know is going to be larger... super silver haze/jack herer, kali mist, burmese, hawaiian sativa, mother's finest, durban poison, haze skunk, NL haze, pure power plant, & sour-D etc. and likely much higher in odor. nothing i've popped was as fast & small as my flumpy's lowdown mystery freebies though which were not at all wanting for resin glands despite the ruderalis lineage & they were so skunky i wouldn't be surprised if the "mystery" were blue cheese or OG kush. i'd like to see that 1 of my last 2 beans of that gets a proper smoke report. it would be a great strain for taming sativa stretch yet another generation removed from ruderalis with a white widow type resin gland yield. i'd be inclined to keep a male cutting of this for breeding compact hybrids leaning to the traits of mother strains. no way i'd ever try and grow a full garden of LM though without an industrial grade carbon scrubber. the ruderalis influence must be bred out in LM as ruderalis is both stretchy & low in odor like a sativa. LM X hindu kush could be a nice commercial pure indica or breeder. with dedicated selection & breeding any annoying trait can be tamed. C99 x LM has serious commercial potential for a 50:50 i'd think and wouldn't be wanting for "skunkiosity" getting cuttings from lowdown mystery could be a pain though as it shows sex quickly & doesn't offer a lot of stem growth. if i ever get a breeding grow working, i'd likely go with a buddha's sister (for it's $ & rarity & cannabis cup genes) or lowdown mystery male over C99 which is easily replaceable. in my first shot at a breeding grow, i intended to C99 everything.