Are there any other manga / anime that managed to place themselves in the Guinness World Records? Or is Eiichiro Oda, with One Piece, the only one so far?
No, One Piece is not the only record holder: as shown in this article, "Kochikame Earns Guinness World Record For Most Volumes Published For Single Manga Series" with 200 volumes.
The ones I could find are:
Now these are just records that I could find in a short span of time. I am sure theres a section for different manga and comics related records.
There is another I'm aware of, although probably not what you were after: Kochikame for the most volumes published for a single manga series.
In a different category (interesting nonetheless), Yu-gi-oh is the highest selling trading card, and 1995 third volume of Weekly Shonen Jump magazine is the highest selling comic magazine. Weird, but fun facts.