Ilford Delta 400. Right speed for general use, while much sharper than Tri-X, especially in solvent developers like D-76. Also more fine-grained, pretty much regardless of developer. Its sensitometric "curve" is very straight, again almost regardless of developer, which yields clean-looking natural images (but I can understand those who like the more interpretive and dramatic look of Tri-X and in particular XP2, which both have S-shaped curves). It's pretty much my only film for both 35mm and 120, though I sometimes use Delta 3200 for speed.
I develop it in a homebrew metol-ascorbic acid developer (derived from the formulas of Patrick Gainer) which yields fantastically fine-grained and sharp images, at the price of some speed loss.