There are several other point-buy character-generation systems for D&D out there (though admittedly it depends on what edition you're talking about). I've long been enamored of
Eclipse: The Codex Persona (affiliate link) for 3.5 and other d20 System-based games, because it not only offers an expansive point-buy catalogue of abilities, but because it also has guidelines on how to alter those abilities, introducing either a minor or major weakness/limitation/drawback to a given ability in exchange for either a price-break or a corresponding increase to another aspect of what that ability can do. The result is that you can make almost any sort of character, from
The Dark Lord Sauron to My Little Pony's
Rainbow Dash.
Having said that, there's a salient aspect to point-buy character-generation (or at least, the aforementioned method of it) that I think often goes overlooked when it's discussed in the context of D&D. All too often, I see a mindset of "how I build my character is my exclusive prerogative, which neither the GM nor the other players can infringe on," and while I understand that point of view, when you have such a flexible method of building characters, there needs to be a greater awareness of how they fit into both the campaign that the GM has designed, and how well they mix with the group's overall cohesion.
Obviously, that's the case for any group's Session 0, but in this case there's special attention called to the fact that the guidelines for altering listed abilities are just that: guidelines. Whether a particular weakness to a power is appropriate (or even possible, within the context of the setting), and how much of a corresponding gain it's worth,
have to be run by the GM and receive their approval. For that matter, the GM may have a blanket disallow of certain abilities altogether. Having such a low-constraints system means that the restraints are offloaded onto both yourself and the other players, not that you're free to do whatever you want without oversight or consequences. Approaching this kind of system with a "if it's in the book, it's allowable for me to use, and no one gets to say boo" is just asking for trouble.
But presuming that everyone is acting in good faith, and has no trouble designing things that are interesting character concepts rather than power-gaming the system, then it can allow for a lot of fun ideas that standard class-level character progressions would have a much harder time with.