For slides, Provia
For B&W, Acros and either Tri-X or HP5+. I'd prefer to stick with one, but sometimes I just have to go with what's available. I have a variety of infrared films in the freezer (HIE, Konica, Maco, Efke, SFX, Rollei) but that's obviously a limited supply.
For C-41, well, I can't even remember when was the last time I shot it. Seven years ago maybe. That said, I hope to try some Portra and/or Ektar this fall when the leaves start to turn.
I've been shooting primarily these four films for years, and using the same developers, but realised I was shooting the same films and using the same developers. So I've decided to try a few alternatives for both film and developers just to see how I like them. For example, the idea of being able to shoot normally and infrared on the same roll of film (Rollei Retro) is very appealing, and means one less camera to carry around. So I'll see how that goes.