Although it is fairly uncommon, there are a few Transformers toys that depict characters that were first seen in some other part of the Transformers franchise. Drift was one such example, having been created for the IDW comics. Spike, the Headmaster partner of the original Fortress Maximus, clearly homages a prominent character from the original cartoon, and is perhaps the earliest example of this trend. Arguably the first toy created for a previously-comics-only character is Jhiaxus.
Jhiaxus was a character created for the short-lived Transformers: Generation Two comic book of the early 1990s (in fact, the name is intended to be pronounced, "Gee-ax-us," in reference to the fate that Simon Furman correctly predicted for the comic book). This toy, a repaint of Beast Machines Jetstorm (and also used for other toys, such as Universe Skywarp), bears practically no resemblance to the Generation Two character, but "Jhiaxus" is the kind of distinctive name that simply doesn't show up by coincidence! The bio given to Jhiaxus in the only edition of the Official Transformers Club magazine to come out from 3H Productions (before the license was given to current club-runner Fun Publications) suggests that the different body was created by Unicron after Jhiaxus was abducted (along with many other Transformers) to serve Unicron's purposes.
Having already featured Skywarp (even if it was nearly four years ago), there's little need to talk about the aspects of this toy that it shares in common with that one. Just click on Skywarp's link above for that stuff. It is, however, worth noting that this version of the mold has some noticeably softer plastic in places, especially the black parts (some parts, such as the head-fins, were soft plastic on other versions of the mold already). Some fans have suggested that this might have been a cost-cutting measure on Hasbro's part, but although at least one other toy from this mold also features this softer plastic, this has never been proven. These toys may be nothing more than a fluke of the era.
When this Jhiaxus toy came out in 2003, it created a fair bit of buzz among the fandom because of the novelty that Hasbro would reference a comics-only character in such a way, even if it was just a repaint that bore little-to-no resemblance to that character (toys such as Drift have demonstrated that Hasbro has been willing to do far more in years since), but that buzz died down after a year or two. However, Jhiaxus hasn't been entirely forgotten. Just this past year, Jhiaxus was the main antagonist in Fun Publications' club comic, featuring this version of the character for the first time in nearly a decade. It's nice to see this character show up again in this form.