In most cases you could simply use a huge number of lines like

  head filename -n 1000000000

or use the "inverse mode". Head and tail can print all but the first/last n lines (I just have trouble to remember without man page the syntax and which does what). So those are more "cat equivalents":

  head -n-0 filename
  tail -n+0 filename

PS: for your wc example you could actually do just

  head -n $(wc -l filename)

because `wc` will print the number of lines and the filename. (does not work with spaces)