Tact switches can be had for four cents each. You should own > 100 of them.
http://www.taydaelectronics.com/electromechanical/switches-key-pad/tact-switch.html
I usually take a wire , connect it to one side ( e.g. the LED in this most basic circuit ), and touch the other side ( in this case the unconnected resistor leg)
Buttons are far too complex with their4 pins; a wire (or two) is way more intuitive, you immediately see if the circuit is closed or not.
Sure, latest when it goes from breadboard to prototype soldering, a free flying wire is not recommended any more, and one should invest in a button ( being as expensive as a transistor, btw )
