Useful to beginners:

• help(1) – help for new users and administrators
• hier(7) – layout of the OpenBSD directory structure
• afterboot(8) – things to check after the first complete boot
• man(1) – display manual pages
• ls(1) – list directory contents
• less(1) – view text files
• kill(1) – terminate or signal a process
• ps(1) – show process status
• top(1) – display and refresh information about the (top) CPU processes
• ftp(1) – FTP program (client)
• lynx(1) – Text-based webbrowser

Useful to intermediates:

• afterboot(8) – things to check after the first complete boot
• netstat(1) – show network status
• dmesg(8) – display the system message buffer
• find(1) – walk a file hierarchy
• locate(1) – find filenames quickly
• sh(1) – public domain Bourne shell
• grep(1) – search for patterns in files
• mount(8) – mount file systems
• df(1) – display free disk space
• du(1) – display disk usage statistics

Useful to more advanced users:

• route(8) – manually manipulate the routing tables
• ifconfig(8) – configure network interface parameters
• fstab(5) – static information about the filesystems
• xargs(1) – construct argument list(s) and execute utility
• awk(1) – pattern-directed scanning and processing language
• dd(1) – convert and copy a file
• strings(1) – print the strings of printable characters in files
• options(4) – miscellaneous kernel configuration options