I suppose the obvious one is Designer 6i. I've been using designer for quite a few years and never had any problems. The only code generation I've done with it was back in my Forms 4.5 days using Headstart which was an abortion at the time. I've heard it's improved since.
As for schema generation, designers fine for that. Infact, I can't imagine doing a DBA job without it. The thought of typing table and index definitions in by hand brings me out in a cold sweat.