Some might prefer to use one with EFKE/Adox films but I've happily used Hypam with these films over the past few years.
So there's no simple answer if you take care with temperatures softer emulsions are ok with non hardening fixers. For me there's no film that requires one.
I don't know of anything that I've seen that "requires" one...but hardening fixer is pretty much "required" by me, personally, since I tend to scratch everything I touch.
I have had hardener ruin negs when developing 8x10 film in a 3005 Jobo Expert Drum -- there would be a permanent mineral-like deposit on the back side of the films.
I'd encourage someone more in the know than me to jump in on this, but my understanding is that 35mm film from Kodak, Ilford or Fuji (and most others) is pre-hardened, and as a result adding hardener at the fixing stage does not improve their ability to resist physical damage - it just makes them harder to wash.
i do work for federal and state archives
and they require NON hardened fixer
because hardener tends to trap in
stuff you want to wash out
if you attempt to do
archival-anything
I think Ian is referring to Hypam as a non-hardening fixer, which I understand to be correct.
Its main difference from Ilford Rapid Fixer is that it will permit the adding of hardener, if one has a special purpose process that requires hardener.
Most modern films are pre-hardened, only a few are softer emulsions. Manufacturers don't recommend a hardening fixer these deays except for extremes likle high process tempertaures.
As Matt says Hypam is a non hardening fixer buffered to be usewd with a hardener if required. In nearly 40 years of using Hypam I've never seen the hardener on a dealers shelf as almost no-one uses it. Ilfotd Rapid Fixer is very similar but with a much lower level of buffering which makes it cheaper to produce. The buffering has no effects on the fixing but the pH must be kept more stable (around pH 5.2 - 5.4 for a hardener to work/
The data sheet for Fuji Neopan 100 Acros (120) (http://www.fujifilmusa.com/shared/bin/AF3-083E.pdf) recommends a hardening fixer. I have seen elsewhere that this film scratches easily. Would using a hardening fixer help?