I just finished doing some developing only to find out my entire strip of film came out blank. The culprit: expired Ilfosol. I thought it looked a little odd prior to developing as it was a dark brown colour, but shrugged it off as I had not used it in months. It wasn't until afterwards did I realize that it was supposed to a be strong yellow colour. A quick search confirmed Ilfosol as having a reputation for dying quickly, though I was unaware of this until just now.
Fortunately there wasn't any of great importance on that roll, just some experimenting with the Holga. If anything, it was a good lesson: stick with Rodinal
Are there other developers out there that have a reputation of short shelf life? XTOL and Ilfosol seem to come up frequently in my searches.