I don't particularly like Kodak films, though I have only used their E6 and C41 stuff. Superia (100) is alright in the right conditions, and I loved the Japanese Reala Ace (which I believe is a slightly different emulsion to the Reala we get in the UK). I love Fuji's E6 range too, with Velvia 100F being my favourite (I know, I'm odd!
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For mono, I find HP5+ ok for walk about use, but it can be too grainy for 35mm. FP4+ is a film I've only used once I think, but the results were so flat and dull I wasn't inclined to try again. I quite like Delta 400, and I have yet to try either Pan F+ or Delta 3200 (which I will probably use in 120 only, given that HP5+ is a bit too grainy for me most of the time in 35mm). I have a few more rolls of Rollei Retro 400 (120) to use up. I find it a lovely film, but it curls like a ******** after development making scanning a pain. Neopan 100 is something I want to keep trying - I think I need to find the right developer to get the best out of it. I only used Neopan Presto 400 the once, but I am tempted to try again with 120, as it had a nice contrast (but was too grainy for me in 35mm).
So, least favourite film? FP4+ or Kodak colour films (in general) - I can't make up my mind.