Part of the fun of using film is trying different film and developer combinations. Rodinal is the the oldest film developers still made, and one of the most popular. It's very cheap and easy to use — you dilute the inexpensive syrup 1:25 or more right before you use it, and it practically has no best-before date.
It does tend to increase the visible grain, so until now I've used it only with low-speed film. On 35mm you'd use it with fast film only if you're looking for a gritty, high-contrast look. But with larger negatives the grain becomes correspondingly smaller. So I recently tried using medium format Delta 400 with Rodinal. The results are really quite good:
This looks great to me. Both the highlights and shadows retain detail even in a high-contrast scene like this. And at full resolution (about 25Mp in this case), where the scanner is already losing image detail, the grain is noticeable, but not at all intrusive:
Here's another image from the same roll:
I like this look a lot. Sharp and clear, without excessive contrast. I'm certainly going to use this combination more in the future. Might even try it in 35mm, just to see what it's like, though I suspect it gets a little grainy for my taste.