I also mostly use other languages these days, but there's still something about C that always feels like coming home to me. Maybe it's because it's what I used during my apprenticeship which is where the magic of programming finally clicked for me (after a failed attempt taking a programming class). Maybe it's just the simplicity and lack of rules to learn.
This is how I feel about assembler. No rules, you on your own. And it is impossible to imagine simpler language. Though I do not write asm lately.