Write a radiation-hardened irradiator
05AB1E, 29 26 bytes

æIg&lt;ùˆ\æIg&lt;ùˆ\æIg&lt;ùˆ¯¯{Å`s


Try it online!, or try all irradiated versions.

The shortest irradiator I could find is 5 bytes:

æ        # powerset of the input
 Ig      # length of the input
   &lt;     # - 1
    ù    # elements of a with length b


The idea is to repeat that 3 times, then do majority voting:

æIg&lt;ù         # irradiate
     ˆ        # add the result to the global array
      \       # pop (in case the above instruction gets irradiated)
æIg&lt;ùˆ\       # idem
æIg&lt;ùˆ        # no pop, it's okay to dirty the stack at this point
¯             # push global array
 ¯            # and again, so at least one goes through
  {           # sort
   Å          # conveniently ignored by the parser
    `         # dump
     s        # swap
              # and implicitly output


Å is a prefix for 2-byte commands, but there's no Å` command, which is why the Å gets ignored. We'll need it later, though.

Sorting makes sure the majority vote is in the middle of the array. Dumping then swapping gets that value to the top of the stack.

Any irradiation in the initial part only results in an error in the global array, which gets solved by the majority vote. Irradiations in the final {Å`s bit are much trickier to reason about:


Å is ignored anyway, so it's okay to irradiate it
If the backtick is irradiated, Å`s becomes Ås, which is the "get middle of the array" extended command.
If { or s are irradiated, that means nothing else is, so the global array is the same value three times. In that case we don't need sorting/swapping, any value will work.