Banner the current line/selection in vim. Uses tcomment plugin once to find the correct comment-style for the filetype.

banner.vim

" banner comments
fu! Banner(opt)
	let l:l1 = line("'<")
	let l:l2 = line("'>")
	let l:spac = indent(line("."))-1
	let l:lines = getline(l:l1, l:l2)
	exe substitute(
				\ substitute('%1d%2', "%1", l:l1, ""),
				\ "%2", l:l2-l:l1+1, "")
	let l:maxim = 0
	for l in l:lines
		if len(l) > l:maxim + l:spac
			let l:maxim = len(l) - l:spac
		endif
	endfor
	let l:s = tcomment#GetCommentDef(&ft)['commentstring']
	if strpart(l:s, len(l:s)-2, 2) == "%s"
		let l:t1 = strpart(l:s, 0, len(l:s)-2)
		let l:t1 = join(reverse(split(l:t1, '\zs')), "")
		let l:s = join([l:s, l:t1], "")
	endif
	let l:bar = repeat('-', l:maxim)
	let l:lines = [l:bar] + l:lines + [l:bar]
	let l:newlines = copy(l:lines)
	let l:i = 0
	for l in l:lines
		let l:l = strpart(l, l:spac, len(l)-l:spac)
		if a:opt == 'center'
			let l:amt_left = l:maxim - len(l:l)
			let l:beg_spac = l:amt_left/2
			if l:amt_left % 2 == 0
				let l:end_spac = l:amt_left/2
			else
				let l:end_spac = l:amt_left/2 + 1
			endif
		else
			let l:beg_spac = 0
			let l:end_spac = l:maxim - len(l:l)
		endif
		let l:temp = join([repeat(' ', l:beg_spac), l:l, repeat(' ', l:end_spac)], "")
		let l:temp = substitute(l:s, "%s", l:temp, "")
		if l:i == 0 || l:i == len(l:lines)-1
			let l:temp = substitute(l:temp, '\s', '-', "g")
		endif
		let l:newlines[l:i] = join([repeat(' ', l:spac), l:temp, ], "")
		let l:i = l:i + 1
	endfor
	call append(l1-1, l:newlines)
endfu
vmap <leader>bb <Esc>:call Banner("")<CR>
vmap <leader>bc <Esc>:call Banner("center")<CR>
nmap <leader>bb V<leader>bb
nmap <leader>bc V<leader>bc