In the cave man days of the last century, there was no such thing as olive pullers. Except in Italy and then it was for the olives you eat not those you put on pipe's.
Most used olives though are knackered and often dented into the pipe itself if superman had been about tightening the back nuts, thinking the tighter they are the less likely they are to leak, not true over tightening usually makes them leak.
We called olives "rings" using the word "olive" for a ring was seen as a sign of a DIY guy not a plumber. If I remember right, its because I think in the Conex compression catalogue they a called "olives" "rings" and a DIY was thought not to read Conex catalogues, which many plumbers did to find the catalogue number of the fittings.
So we would use a combination of tricks to get the olive, i.e. spanner behind back nut and knock the olive off, hacksaw as already explained, piece of wood and tap the olive downward with it.
Surprising as it may seem a piece of wood often worked the best, while it didn't look as though it would. It didn't leave all them scrape marks from the spanner or footies on the pipe either. Its a bit of a knack to it of course, and some guys could get nearly any olive off with one or two knocks.
We would often also look for replacement olives made of copper or soft brass, of the same size of course, simply because they would squash down easier onto an out of true pipe end.
The old Honeywell three port valves had olives/rings in them so hard, you needed a pair of Stilsons to tighten them up, to stop them from leaking.
The modern olive pullers, seem okay I have never tried them though, usually spent the cash on something else.