The amplifier is the most important piece of guitar related hardware.

1. Counter argument

1.1. The guitar is the most important part

1.1.1. Almost useless without an amp to change the sound quality (useful for different genres of music)

1.1.2. Uses pickups on the guitar, but they are useless without the amp

2. Historical

2.1. One of the pioneering engineering feats to lead to rock n' roll

3. Vast array of sound options

3.1. Amps have different options of "effects"

3.1.1. Modulation

3.1.2. Delay

3.1.3. Reverb

3.2. Different amps = different sounds

4. Different types

4.1. Digital (Bias FX)

4.2. Vacuum tube

4.3. Solid state

4.4. Hybrid

4.5. Modeling

4.6. Acoustic

4.7. Bass

4.7.1. Different entity b/c of lower pitch and distortion