For hiking, we need a lightweight flashlight with a long run time. Also, the flashlight should have a good combination of flood beam for close distance lighting and focused beam for further distance lighting.
Generally, flashlights with very high brightness and long throw distance have a relatively short run time, these kind of flashlights are not ideal for hiking.
High speed cycling at night requires a flashlight / bike light with high output and wide flood beam to light up the road ahead. Also a long run time is necessary.
It will be great if the flashlight / bike light can work continuously for several hours. Last but not least, you should consider whether the flashlight / bike light is convenient to operate while mounted on the handlebars of the bicycle.
For the hostile caving environment and low reflectivity of rocks in caves, a high-brightness flashlight is an essential piece of your equipment.
Also, good water resistant ability is needed for wet cave environments. Some emergency situations require the flashlight to have good shock resistance performance to assure it works normally after impacting rocks or drops.
Diving flashlights require completely waterproofing and extremely reliability as well as high brightness. A reasonable run time is enough, depending on what type of diving activities one intends to do.
Generally, the larger diving flashlights are easy to hold / grip. The switch should be able to resist high water pressure (rotating switch or toggle switch is preferred). Also, a non-slip and extra large lanyard is necessary.