Nokia C250.
It's a big permanent-installation mobile phone.
Powerful 3-watt transmitter connects to cell towers even from way out in the fringes where no hand-held phone can connect.
It's analog, so much better sound quality than compressed digital. The audio just goes a little fuzzy, but never drops out either like digital does, when the signal gets bad.
Being analog, it can also carry modem tones, so you get data connectivity using your voice plan. Much cheaper than subscribing to a special "data plan" like you have to with a digital phone.
It also runs on the dirtiest power known to mankind... 12 volts from a car's electrical system, ignition noise and everything, without ever shutting down, locking up, or interfering with the audio.
And the backlight stays illuminated continuously (unless the phone is turned off).
It's the most reliable and robust cellular telephone I have ever seen.