Maybe it's already mentioned somewhere here, but since the cat didn't know it, have another recommendation:
Basically it will show you everything you have on any of your chars or in your bank, which is highly useful if you don't want to log thru 15 of them to find out who has your duplicate Worm Cult Chest piece or your precious Shadowsilk Gem.
You can filter your inventory by item type, search for specific things, see all the currencies everyone has, count your writ vouchers, and there's a motif check too.
Today is the last day of our costume contest. Don't miss your chance!