Ideas for a short game coding party

Hi,

I'm planning the next LTGameJam party, and some interesting ideas for the
games/engine are needed. We've though some, but more would be welcome :)

Short description of the party: LTGameJam (http://jammy.sourceforge.net);
which is in turn similar to IndieGameJam (http://www.indiegamejam.com/), is
a short game development event. Someone prepares a small specific "engine",
invites a bunch of game programmers/designers, and over two days they try to
make small games. Of course, two days to study the engine and write a game
is a very short time, so main focus should be on original ideas, etc. We've
made two Jams already, first being direct IGJ0 clone - "100k game units!",
second being "physics, cars and stuff". Now, it's time to think of the idea
for the next one...

If anyone has a crazy idea and is willing to share it, you're more than
welcome. Anyone willing to participate is welcome also, though so far
LTGameJam was in Lithuania (hence 'LT'), and only Lithuanian programmers
were participating (but noone enforces that :)).

Here's a short list of ideas currently "in processing":

1) Old maze-like games. This is simple and easy, but not very original or
interesting. Basically, it's 2D maze at logic level, with engine providing
pathfinding, collision, entities, particle effects, camera etc. The
participants take this "2D maze" thingie and write some game logic.

2) "guess the packet" network games - there's a server that basically just
broadcasts packets. And there are clients. The twist is, that while client
games use the same server and same physical packet structure, they don't