$PS1

For many years I used one and the same PS1 prompt on all computers I had:
PS1='\u@\h:\j:\w\$ '
It looks like this when rendered:
slava@jupiter:0:/usr/local/bin$
Simple and functional, but when dealing with large outputs (say, compiling a C++ program...) it might be hard to find the start of the output, the prompt simply dissolves into the wall of text.

Not long ago I changed my job and decided it was time to update my PS1 as well. I wanted something with better contrast and readability. The result was this:
if [ `id -u` -eq 0 ]; then PS1='\[\e[1;31m\]┌─<\w>\[\e[0m\]\n\[\e[1;31m\]└▶\[\e[0m\] ' else PS1='\[\e[1;32m\]┌─<\w>\[\e[0m\]\n\[\e[1;32m\]└▶\[\e[0m\] ' fi case "$TERM" in *rxvt*|*xterm*) PROMPT_COMMAND='echo -ne "\e]0;' if [ `id -u` -eq 0 ]; then PROMPT_COMMAND="${PROMPT_COMMAND}#" else PROMPT_COMMAND="${PROMPT_COMMAND}\$" fi PROMPT_COMMAND="${PROMPT_COMMAND}"' ${PWD/#${HOME}/~}\007"' export PROMPT_COMMAND ;; esac
This is what it looks like on screen:

This prompt is highly visible, turns red when you switch to root user and has the good property of always having the cursor in the same place.

A few days ago I installed good ol' OpenBSD as my main OS on my main PC and I think I came up with an even better prompt:
export COLUMNS export PWD PS1='\[\e[1;30;47m\]`awk "BEGIN { n_cols = int(ENVIRON[\"COLUMNS\"]); txt = ENVIRON[\"PWD\"]; line = \" \"; line_len = length(line); n = n_cols - length(txt); printf(\"%s\", txt); for (i = 0; i < n; i += line_len) { printf(\"%s\", substr(line, 1, n - i)); } printf(\"\\n\"); }"`\[\e[0m\]'
This is what it looks like:

Neat, huh?