I think I need to clarify what an IBL is.

Any strain can potentially BECOME an IBL over time if it is bred and stabilized for long enough, and all the instances of phenotypes that do not represent the desired strain traits are discarded and not used for breeding. This takes many generations of work to accomplish, but in the end, the result is that anyone can make their own seed crop from the beans they get.

Most strains on the market are F1 hybrids, or strains that may or may not be fully stable, but the seeds are being bred from only a very specific breeding pair of individual plants, and are predictable. Some breeders, such as Subcool, don't even wait long enough to assure little to no phenotypic variation among the generation being sold in seed form, and the resulting plants can be all over the place! Space Queen had a reputation for throwing the most outrageous assortment of phenos- not good if you wanted to run crops off from seed, but acceptable if you had intended to pick a favorite phenotype and save her as a mother.

Popular strains that are currently available from seed vendors that are true IBLs include Island Sweet Skunk, Power Plant, and Donkey Dick. The BOG's Bogglegum was so stable at the time of his retirement that it can very nearly be considered an IBL as well.