bzcat (1)            - decompresses files to stdout
ip6tables-save (8)   - dump iptables rules to stdout
iptables-save (8)    - dump iptables rules to stdout
putchar (3p)         - put a byte on a stdout stream
putwchar (3p)        - put a wide character on a stdout stream
stdout (3)           - standard I/O streams
stdout (3p)          - standard I/O streams
zipnote (1)          - write the comments in zipfile to stdout, edit comments...