Random update:

I am currently in the process of writing a software that might severely damage your data if I make a mistake, so I wouldn't feel well with a license without a warranty clause at least this time - no WTFPL this time (and the WTFNMFPL looks fishy - two clauses contradicting each other, eww).

The ISC/MIT license would be an option, but they still add one "YOU MUST", namely the need to keep my copyright notice/license/whatever. I don't care about that, especially as it annoys me a lot to add a whole rat's tail of CAPITALIZED law prose to my code if I want to use some other people's libraries. If you'll ever find yourself in my position and you don't absolutely need juvenile wordings with slight legal ambiguity, the 0BSD or MIT-0 licenses might be worth a look:

https://spdx.org/licenses/0BSD.html#licenseText
https://spdx.org/licenses/MIT-0.html#licenseText

I think I'll use these a lot in the future.