Kodachrome was my slide of choice. Still some to burn, about 11 rolls now.
Generally though, I like Fuji Pro 400H and 160S. I've tried Portra and it's very nice but I prefer Fuji.
For general film use, I'm increasingly turning to Kodak Gold (100-400) which is nice and warm, good for the subjects I tend to do on these films which are portraits, quite a few of children and it suits the whole 'thing' 🙂 Whatever the thing is.
For good punchy almost Kodachrome replacement I use Ektar (shame you can't project it...) which is just wonderful. I would use it more but it's not a slide film. Still, it's an incredible C41 film.
Slide use, well I tend to go for Elite Chrome Extra Colour, but I also use Velvia 50, but quite sparingly as it is very contrasty and whilst I like what it can do, I prefer something a little more balanced. Of course, a 6x6 Velvia transparency exposed well is lovely.
I'm tending to shoot 160S/400H more in 120 as prices for 35mm 400H/160S are quite high, about £4 a roll (incl postage) -- but I do love shooting it in my M2.
Sometimes I find myself thinking "You know, it's time you took a look at that GF1, or EOS 40D or whatever again." Then I look at prints from 160S and 400H and think, naaaaaaaah!
Vicky