Consider the situation where a subset of the population in modern times has a power that allows them to consume their life to temporarily increase their speed and/or strength. In a fight, what weapons would they use?
Details about the power
The power works by removing time from the end of a person's lifespan equal to the number of copies of them it would take to do the thing, either serially or in parallel multiplied by the length of the activity. For example, if someone with this power is walking at a pace where it takes 20 minutes to go 1 mile and wants it to take 2 minutes instead, it would take 10 of them to cover the mile (the original plus 9 copies). Thus, the lifespan consumed would be 18 minutes (2 minutes per copy times 9 copies). Similarly, if someone can ordinarily lift 50 pounds and wants to lift a small car (~2000 lbs), it would take 400 of them to do so. A minute of walking around carrying a car would consume 399 minutes (399 copies times 1 minute).
Speed and strength increases require separate copies. So picking up a small car and carrying it as far as one could normally carry 50 pounds in 5 minutes in a minute would consume 19999 minutes of lifespan. It takes 20000 people to cover the given distance in a minute with the load, so there are 19999 copies.
The upper limit to the speed and strength increases is the amount of lifespan available. At any speed, the person can still perceive the world around them normally.
If someone attempts to do something and doesn't have enough lifespan left to do so, they die.