Flying Carpet

Hold jump once your other jumps are spent and you lock onto an invisible horizontal rail. There is no upward push at all, so whatever height you start at is the height you keep. Let go and you drop, and you can catch the rail again lower down as long as there is time left on the clock.

It sits in a Pyramid chest, which means you can have it before beating anything. Paired with a grappling hook it covers ground in a way nothing else pre-hardmode manages: hook up, run the carpet out, hook again. It also carries you straight over single block steps and staircases instead of hopping each one, which quietly makes cave exploring less tedious. It is also the easiest way to catch a gliding critter, since you can park at their altitude and wait.

A flat horizontal float is a poor dodge against anything that shoots straight, and an excellent platform for shooting back. Bring a ranged weapon, stay level with the target and strafe. The clock is short, so treat every activation as one pass rather than a hover you can settle into.