The tools above are fine, and might make sense if you plan to remove cotters on a regular basis. However they are not necessary and even when cotters were SOP on 95% of cranks, many mechanics, even pros do without.

The tools needed to remove cotters are knowhow, hand skill, a hammer, and something to dolly the crank.

Here's how I do it -- works every time.

1- find a length of pipe long enough to reach from the crank arm to the ground, or something to use as an anvil, ie. bench vise.
2- back cotter nut off 2mm or so.
3- brace the dolly (pipe) under the crank so that any hammer blow delivered will not be dissipated by the crank "rolling with the punch". Good bracing of the crank is key because that's what concentrates the hammers energy in the pin.
4- deliver a solid blow to the pin and it'll move. This isn't a process of tapping it out, but driving it half way to China with a single shot. Solid blos move the pin, weak blows just mushroom the end.

4.5-- if you have doubts about your hammer skills, or are afraid you might hit the chainring, hold a punch against the cotter and drive it with that.