An addon to automatically summon vanity pets and mounts randomly, with percentage weights applied to the random-generator applied based on continent, zone, spec, and possibly other variables (so that, for example, Frosty gets summoned more often in Northrend by 10% while in snowy zones, or the halloween mount gets summoned semi-randomly all the time, but 100% of the time during Hallow's End, or whatever the user decides to come up with).

My biggest hurdle will be designing the GUI. I'm planning on it being a GUI config screen that ties in directly with the companion tab, so /commands won't be necessary.