I like multi fuel lights. Just about any D cell device can be fed with AA's with an adapter, C cells only require a simple spacer tube to run AA's because AA's are about the same length as C cells. There are also 4D to 6 Volt adapters for 6V lanterns.
Streamlight's 1L-1AA and Compact II are designed to run on AA's or CR123's and AAA's will work as well.
The most versatile lights with regards to batteries that I have are an old 2D Mag and a 2D Fulton moonbeam with Nite Ize 74 and 55 lumen LED drop ins which will accommodate 2 to 9 Volts and with some adapters that I 3D printed I can use:
2 D cells
2 C cells (in 2D to 2C adapter)
1 18650 (in 2C to 18650 adapter with the 2D to 2C adapter)
2 CR123's or 2 16340's (using the above adapters)
2 AA's or 2 14500's (in 2 C to 2 AA adapter).
2 AAA's or 2 10440's (in above adapters with a 2 AA to 2 AAA adapter sleeve)
- that's 9 different battery types, not counting similar variations such as 16 or 17650s or a few odd battery sizes which I have not tried, but would likely work, such as 3 N batteries in place of 2 AA's or 3 CR2's in place of the 18650.
Again, this is made possible by the Nite Ize drop-ins which will handle the Voltage range of these battery combinations.
Charles Artificer on youtube took all of this to the next level with adapters he made out of lathe turned PVC:
…. and with a 1-9 Volt LED drop-in and an improved set of adapters he made can even run on single 1.5 Volt cells and 9 Volt batteries!