I'll put in the list those I've found so far and where if they were new to me:
| Designator | Component | Notes |
|---|---|---|
| BT | Battery | |
| C | Capacitor | |
| CE | Electrolytical capacitor | On a Saturn controller |
| CN | Connector | |
| CR | Diode | On a Sega Saturn power board |
| CR | Programmable Unijunction Transistor (PUT) | On a PC-8801FE power board |
| D | Diode | |
| D | Zener diode | Sometimes they're maked with "D" instead of "ZD" |
| EM | Electromagnetic Interference (EMI) filter | On a Mega Drive board |
| F | Fuse | |
| FB | Ferrite bead | |
| IC | Integrated circuit | |
| ICA16 | Integrated circuit | "A" because there's a "B", and "16" because how many pins it has; on a SNES controller |
| JA,JC,JE | Jumper | On a PS2 power board |
| JP | Jumper | |
| L | Inductor | |
| PC | Optocoupler | From "photocoupler"; on a PS2 power board |
| Q | Transistor | |
| R | Resistor | |
| R | Resistor network | On a Hudson Famicom Controller |
| RFC | Radio Frequency Choke | A type of inductor; on a NES RF switch |
| SA | Variable Resistor | Japanese Sega Saturn PSU Type-A |
| T | Transformer | |
| TC | Trimmer capacitor | On a SFC board |
| TH | Thermistor | On a PS2 power board |
| TR | Transistor | On Mega-CD 1 power/audio board |
| TP | Test point | |
| U | Integrated circuit | |
| VR | Variable resistor | Trimpot found on a PC-8801FE power board |
| X | Crystal oscillator | On a NES |
| ZD | Zener diode |