This started as a topic on flickr but I think it'd be interesting to see what people like to use here too. I'll start with my top 3:
1st:
Ilford pan f+Here shot with a Lubitel 166U
A bit expensive but since it's so low iso it ages well and you shouldn't be afraid of snapping some up if you find some expired rolls.
I've seen it mostly used for portraiture and it can be hard to get the amount of light you need with toycameras like the holga or diana. It can be a challange. But when you push yourself you can get some fantastic results!
Works good with the onboard holga flash I'd say
2nd:
Foma Fomapan 200 "Creative"Here shot with an old box camera that I flipped the lens on.
All round good film -and pretty cheap too!
I've heard friends complain that their holga shots look too much well exposed even! It has just got a wide range and I think that is really good for experimenting with new cameras and mods.
3rd:
Fuji Neopan Acros 100, or as I call it just: AcrosHere shot with a folding 6x9 camera modified to pinhole (I call it the À la Lynch!)
Looking to try long exposures in black and white? Acros is your friend~
Before I would think a higher speed film like Ilford HP5 would be better for long exposures, hugely mistaken. I quote:
"Ilford HP5+, start compensating from 1/2 second; at 5 seconds, it's already more than 1 stop. Delta 100, same story."
And Acros? "No correction below 120 seconds, +1/2 stop between 120 and 1000 seconds."
Going into second long exposures and beyond Acros is more capable of gathering more light, perfect for pinhole for example!
Well, that's from me. Different films for different situations you could say. But often I just have one kind of film and make that work there and then.
Now how about you?