XOR gates make nifty oscillators too, from AF to HF. PotatoSemi (yes, potato chip) makes GHz speed 7400 series equivalents. It would be fun to see what logic at such levels could make possible for RF.

The optoelectronic logic element, Figure 1, contains three input control switches of optoelectronic pairs U1.1, U2.1 …U6.1 (optronic pairs are highlighted in color for clarity), made on transistors Q1 ...

There usually follows a demonstration of simple AND, OR, and XOR gates made from NAND gates, ... This means you can have a universal gate as a ROM constructed with only diodes.