Will toggle view between regular and hex editor. Unfortunately switching between these views somehow modifies the file. It'd be great if it haven't had any side effects. Maybe someone knows a better way to do it.
noremap <F10> :call HexMe()<CR>
let $in_hex=0
function! HexMe()
    set binary
    set noeol
    if $in_hex>0
        :%!xxd -r
        let $in_hex=0
    else
        :%!xxd
    let $in_hex=1
    endif
endfunction