So many lines to choose from, but the ones I wouldn't be without and would highly recommend for all vimmers:
" remap jj to escape in insert mode
inoremap jj <Esc>
" swapping : and ; save a lot of unneeded shifting:
noremap ; :
noremap : ;
" The wish that grants more wishes (edit vimrc with \ev)
nnoremap <Leader>ev :tabnew<CR>:e ~/.vimrc<CR>