58mm uv filter
I don't need it to be anything special just something that if it gets a scratch I can throw out rather than live with a lens withe a scrape in every picture I take.
As others have said, you are much more likely to have bad stuff in every picture you take if you keep a cheap filter on at all times.
Myself, I bought B+W U/V filters for all my lenses (including my 18-55 kit lens), but I only use them when I am at the beach and there is blowing sand and ocean mist. I use hoods for protection (including on my 18-55 kit lens.)
Hoods always; filters, only when needed.