Not only crystals make suitable LOs, VXOs or super-VXOs, there are also VFOs designed with ceramic resonators. VFOs with ceramic resonators are not stable enough for QRSS or WSPR, however, CW or SSB do not require the same VFO stability as the digital mode.
Some resonator frequencies (MHz) I know about:
- 2.00
- 3.58
- 4.00, 4.03, 4.16, 4.19, 4.50, 4.91
- 5.00, 5.50, 5.74
- 6.00, 6.50
- 8.00, 8.64
- 10.00, 10.70
- 12.00
- 16.00
In combination with some crystals, those resonators would make some awesome VFOs.