Many years ago, when I was but a fresh faced idiot, the partition that contained the mSQL database which had All The Data filled up. I moved it into /tmp because there was plenty of space.
For those who don't know, solaris uses tmpfs for /tmp. It is a virtual memory/swap based file system. Anything in /tmp is actually temporary if the machine reboots/powers off.
I like setting this up on Linux machines too. There are tons of ephemeral files that get written there, depending on your usage case, and I'd rather not waste the IO for writing pids to lockfiles. Disk is cheap, but RAM is fast and cheap. :)
On a Solaris box.
Hilarity ensued when we next rebooted it.