two piezo elements, such as Digi-Key part #102-1126-ND or #478-4764-ND (Either is fine; I used one of each.)
two small paper clips
an LM386 op amp IC
an 8-pin IC socket
two 10k ohm variable resistors (i.e., potentiometers or pots, preferably audio tapers, not linear tapers; see Audio Tapers vs. Linear Tapers in Building It for the distinction)
two control knob covers (RadioShack part #274-415 is a good buy.)
two 10k resistors (coded with brown-black-orange stripes)
a 100 μF electrolytic capacitor
an 8–1000 ohm audio output transformer, such as RadioShack part #273-1380
a spring (light, thin gauge and roughly 3″ or 4″ long when at rest)
two 1/4″ mono phone jacks (guitar jacks)
a 9-volt battery clip
a 9-volt battery
24-gauge insulated hook-up wire
a small SPST switch, such as RadioShack part #275-612
pieces of sturdy corrugated cardboard or a small cardboard box around 6″ long
a largish, sturdy enclosure (A cigar box works well, since the reverb tank will take up a good deal of space.)
(optional) 22- or 24-gauge bare bus wire