As I argued last week, using an event like Halloween to gain marketing leverage when you update your game may not be a the most sensible approach.
It's only a single day, and every other developer is doing it.
Irish developer Tribal City has been thinking along the same lines as me. Its latest game is designed around a month-long global event.
Doing a Selleck
In support in the hairy top lip month of Movember, 'Tache is a game with a charitable objective.
You play control a moustache who gets points for his proximity to moving razor blades, in single and multiplayer modes, with the 99c, 69p, €0.89 price being donated to the Movember charity (net of Apple's 30 percent margin).