group.vim

function! Group()
    normal! l"ry$"ly0
    redir => message
    execute "silent %g/\\V" . escape(@l, '/') . "/d"
    redir END
    let cnt = matchstr(message, '\d\+')
    execute "normal! ggO" . cnt . ' ' . @l . ' || ' . @r . "\<Esc>0"
endfunction

nnoremap <silent> <leader>g :call Group()<CR>

Group similar lines around the cursor, similar to uniq -c. Example:

this is unrelated
some prefix, some details
some prefix, other details
some prefix, even more details
another prefix

With the cursor in front of other details press \g to group all lines sharing the prefix left to the cursor, leaving the text to the right as example details:

3 some prefix, || other details
this is unrelated
another prefix

This is useful to quickly group tons of lines into similar groups based on common prefixes.