I noticed Control-C had stopped working on my Linux box for killing foreground processes. I’m not sure how it happened but somehow my stty intr setting got set to Control-G. Here’s how I diagnosed it and fixed it:
$ stty speed 38400 baud; line = 0; intr = ^G; erase = ^H; eof = ^A; eol = M-^?; eol2 = M-^?; -iexten $ stty intr ^C