There are lots! Too many to cover in a single HN comment, and this space is evolving rapidly so I encourage you to look around.

While the coding assistants are pretty much universally free, you still need to connect them to a model. The model tokens generally cost something once you've gone past a certain quota.

I'm not sure if this is still true, but if you have a Google account, Gemini Code Assist had a quite generous "free tier" that I used for a while and found it do be pretty decent.