Specifically, a network drive that I previously mounted manually for a one-time operation and now tries to re-mount every time I login.
The drive is not setup as a login item in my accounts pref pane, nor has it ever been.
In response to the comments:
I don't run any apps from the share. It's a network drive I don't normally use, I just mounted once to get some data of it.
I initially mounted it just by using the 'connect to sever' option in finder.