This works for any weapon that has channel and auto reuse.Ice Bow and Flying Knife are looking like solid A tier weapons right now.
Some of you may be aware about the Flying Knife + Yoyo glitch.
Turns out, for some reason, it actually works seamlessly with the Ice Bow as well, and it's the ONLY pre-mech bow it works with for some reason. Later on it works with Phantom Phoenix and Phantasm (more on that later) as well, but that's it. You don't even need autoswing from Feral Claw to make it work, unlike with Yoyos.
This means two things: 1. Flying Knife provides extra damage, especially against multiple enemies and worms. No i-frame issues. 2. Flying Knife can use Ichor Flask to increase Ice Bow's damage.
The armor you'd want to use this with is obviously Frost Armor, and not just because it coincidentally fits thematically. You can achieve over 1000 DPS on grounded targets, especially slow and/or large ones.
There's also Phantasm to consider. Want to use other arrows that aren't Ichor Arrows while still having enemy defense lowered? The answer has arrived at last. I'm planning on making a video about this on my channel in the near future but for now I'll share my knowledge in this thread
The knife projectile's ai checks if you're channeling, which means you are holding down left click and are holding a weapons that has channel. So for example Laser machinegun has channel so you can switch to it while holding the knife.
However laser machinegun doesn't have auto reuse so it won't start firing until you reclick which cancels the channel sending the knife back, this is why you need auto reuse.
in addition to the examples @AngryNimbus found drills and chainsaws also work.
The reason this works for flying knife and not most other channel weapons is because flying knife doesn't force the player to animate, you can do this with magic missile type weapons too but thier projectiles have limited pierce.
I checked the source code and ice bow for some reason has channel... I have no idea why it does it doesn't use it for anything, channeling is used for stuff like yoyos and animated weapons like LMG and phantasm. Ice bow is neither of those it's one of the most boring weapons in the game... or at least it used to be. Maybye at one point it was supposed to do something more interesting.