LotR -- Book 3 - Chapter 09 - Flotsam and Jetsam

[Boromir88]

And are there any other people who could resist Saruman's voice?

I would say Gimli, because "they (Dwarves) are not evil by nature, and few ever served the Enemy." The dwarves were a resiliant race and basically told Sauron to bug off, despite being offered riches, land, and an "I'll leave you alone" pass. It is also Gimli who first rejects Saruman in the next chapter, as well as the previous chapters we see his fond hate for the man. Now if you give it some time, Saruman might get to Gimli. But I would say if you don't restrain Gimli he'd try to chop off Saruman's head (or legs) before Saruman corrupted him.