credits to Yegappan Lakshmanan's Displaying the current Vim environment
:abbreviate - list abbreviations
:args - argument list
:augroup - augroups
:autocmd - list auto-commands
:buffers - list buffers
:breaklist - list current breakpoints
:cabbrev - list command mode abbreviations
:changes - changes
:cmap - list command mode maps
:command - list commands
:compiler - list compiler scripts
:digraphs - digraphs
:file - print filename, cursor position and status (like Ctrl-G)
:filetype - on/off settings for filetype detect/plugins/indent
:function - list user-defined functions (names and argument lists but not the full code)
:function Foo - user-defined function Foo() (full code list)
:highlight - highlight groups
:history c - command history
:history = - expression history
:history s - search history
:history - your commands
:iabbrev - list insert mode abbreviations
:imap - list insert mode maps
:intro - the Vim splash screen, with summary version info
:jumps - your movements
:language - current language settings
:let - all variables
:let FooBar - variable FooBar
:let g: - global variables
:let v: - Vim variables
:list - buffer lines (many similar commands)
:lmap - language mappings (set by keymap or by lmap)
:ls - buffers
:ls! - buffers, including "unlisted" buffers
:map! - Insert and Command-line mode maps (imap, cmap)
:map - Normal and Visual mode maps (nmap, vmap, xmap, smap, omap)
:map<buffer> - buffer local Normal and Visual mode maps
:map!<buffer> - buffer local Insert and Command-line mode maps
:marks - marks
:menu - menu items
:messages - message history
:nmap - Normal-mode mappings only
:omap - Operator-pending mode mappings only
:print - display buffer lines (useful after :g or with a range)
:reg - registers
:scriptnames - all scripts sourced so far
:set all - all options, including defaults
:setglobal - global option values
:setlocal - local option values
:set - options with non-default value
:set termcap - list terminal codes and terminal keys
:smap - Select-mode mappings only
:spellinfo - spellfiles used
:syntax - syntax items
:syn sync - current syntax sync mode
:tabs - tab pages
:tags - tag stack contents
:undolist - leaves of the undo tree
:verbose - show info about where a map or autocmd or function is defined
:version - list version and build options
:vmap - Visual and Select mode mappings only
:winpos - Vim window position (gui)
:xmap - visual mode maps only