I don't place much importance on the language used, but then my team uses a bunch of different programming languages because we integrate existing systems more

I don't place much importance on the language used, but then my team uses a bunch of different programming languages because we integrate existing systems more than we write new ones from scratch. However, I do think the language choice itself says a lot about the person. If they reach for C, they're probably more interested in systems programming. If they reach for Ruby, they're probably more interested in web app development. If they reach for Bash, they're probably interested in SysAdmin-type work. Does their language choice reflect an interest in the job they're applying for? If it's reasonable to expect the person to know multiple languages well (i.e. they're not doing their first internship in college or something) I also want to see them pick an appropriate tool for the job. What I'm really looking for, is if the language they know best is actually a language they know well. If it's not, that's a red flag to me. I wouldn't say it's bad to do an interview in C# when applying for a job at a Java shop, but all other things being equal, using Java would be better, IMO.