my tmux config (updated for 2.4)

tmux.conf

# This requires tmux 2.1. a lot of these settings will error on anything earlier.

# Act like Vim; use h,j,k,l to select panes and move the cursor
set-window-option -g mode-keys vi
bind-key h select-pane -L
bind-key j select-pane -D
bind-key k select-pane -U
bind-key l select-pane -R

# Look good
set-option -g default-terminal "xterm-256color"

# macOS bash only: connect to user namespace
# (http://www.economyofeffort.com/2013/07/29/reattach-to-user-namespace-the-fix-for-your-tmux-in-os-x-woes/)
# set-option -g default-command "reattach-to-user-namespace -l bash"

# Enable mouse support (works in iTerm)
set-option -g -q mouse on

# make mousewheel work when not in copy mode
bind-key -T root WheelUpPane if-shell -F -t = "#{alternate_on}" "send-keys -M" "select-pane -t =; copy-mode -e; send-keys -M"
bind-key -T root WheelDownPane if-shell -F -t = "#{alternate_on}" "send-keys -M" "select-pane -t =; send-keys -M"
# bind-key -t vi-copy WheelUpPane halfpage-up
# bind-key -t vi-copy WheelDownPane halfpage-down

# scrollback buffer size increase (this eats up memory, sometimes)
set -g history-limit 500000

# C-b C-b will swap to last used window
bind-key C-b last-window

# Start tab numbering at 1
set -g base-index 1
set-window-option -g pane-base-index 1

# Allows for faster key repetition
set -s escape-time 0

## Color Shit

# Highlight active window in tab-bar at bottom in grey
set-window-option -g window-status-current-style 'bg=#151122 fg=#e0af68'
set-window-option -g window-status-current-format ' #I:#W '

# purple status bar
set-option -g status-style 'bg=colour54 fg=white'
set-window-option -g window-status-format ' #I:#W#F'

# border colors
set-option -g pane-border-style 'fg=color18'
set-option -g pane-active-border-style 'fg=colour54'

# command mode
set-option -g message-style 'fg=#e0af68 bg=black'
set-option -g message-command-style 'fg=#e0af68 bg=black'
set-option -g mode-style 'fg=black bg=#e0af68'

## end color shit

# set -g window-style 'fg=default,bg=default'
# set -g window-active-style 'fg=default,bg=default'
# set -g pane-border-style "fg=green,bg=default"
# set -g pane-active-border-style "fg=default,bg=default"
# set -g pane-active-border-fg colour51

# use different keys to split vertical and horizonal
# ^B | for vertical split
# ^B - for horizontal split
bind | split-window -h -c "#{pane_current_path}"
bind - split-window -v -c "#{pane_current_path}"

# Change cursor in vim to distinguish between insert and command mode
# Use in conjunction with tmux-cursors.vim
#set-option -g terminal-overrides '*88col*:colors=88,*256col*:colors=256,xterm*:XT:Ms=\E]52;%p1%s;%p2%s\007:Cc=\E]12;%p1%s\007:Cr=\E]112\007:Cs=\E]50;CursorShape=%?%p1%{3}%<%t%{0}%e%p1%{2}%-%;%d\007'
set-option -ga terminal-overrides ',xterm-256color:RGB'

# use C-b v to paste the tmux buffer
bind v paste-buffer

# clipboard stuff for OSX
# be sure to `brew install reattach-to-user-namespace` to use this
# ^B ^C to set system clipboard to tmux's
# bind C-c run "tmux save-buffer - | reattach-to-user-namespace pbcopy"
# bind C-v run "tmux set-buffer $(reattach-to-user-namespace pbpaste); tmux paste-buffer"
bind p paste-buffer
bind -T copy-mode-vi 'v' send -X begin-selection
bind -T copy-mode-vi 'y' send -X copy-selection

# show battery status in status bar. comment this out if you don't need it
# gem install batt
set-option -g status-right-length 120
set-option -g status-right "[ #(batt meter --tmux --size 10) #(batt capacity) ] #(date \"+%Y-%m-%d %H:%M\")"

# renumber windows (if you have gaps in numbering, this renumbers them sequentially
# ^B r
bind r movew -r

# split the screen into a main screen and an 80-width pane on the right
bind -n C-g split-window -h -c "#{pane_current_path}" \; resize-pane -x 80 \; select-pane -t 0

# split the screen into main screen with 16-tall pane on the bottom
bind g split-window -v -c "#{pane_current_path}"\; resize-pane -y 16# \; select-pane -t 0

# move current window left and right in the tab list, respectively.
bind '<' swap-window -t -1 \; previous-window
bind '>' swap-window -t +1 \; next-window

# ^B \ : resize the currently selected pane to be 80 columns
bind '\' resize-pane -x 80

# ^B ] : resize the currently selected pane to 16 rows high
bind ']' resize-pane -y 16

# Smart pane switching with awareness of Vim splits.
# See: https://github.com/christoomey/vim-tmux-navigator
# is_vim="ps -o state= -o comm= -t '#{pane_tty}' \
    # | grep -iqE '^[^TXZ ]+ +(\\S+\\/)?g?(view|n?vim?x?)(diff)?$'"
# bind-key -n C-h if-shell "$is_vim" "send-keys C-h"  "select-pane -L"
# bind-key -n C-j if-shell "$is_vim" "send-keys C-j"  "select-pane -D"
#bind-key -n C-k if-shell "$is_vim" "send-keys C-k"  "select-pane -U"
# bind-key -n C-l if-shell "$is_vim" "send-keys C-l"  "select-pane -R"
# bind-key -n C-\ if-shell "$is_vim" "send-keys C-\\" "select-pane -l"

@spikegrobstein

Just a note, I ran into a minor issue setting up a new machine.

reattach-to-user-namespace needs to be installed or ln15 will cause tmux to immediately exit.

brew install reattach-to-user-namespace

@spikegrobstein

Per our convo, ln40 need to be update to the following for tmux 2.9

set-window-option -g window-status-current-style "bg=red"