One way to get a neat, "tubelike" sound is to run a CMOS 4096 inverter biased as an opamp. One 4096 will give you six amplifiers and they give a very pleasant, "warm" sound when overdriven.
Hanging on my wall is a nice Ibanez, LesPaul Sunburst that has suck an amplifier built in (switchable of-course). It will even drive a headphone directly.
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