@yee: We actually did a tourney much like that one once, right after SoSe was introduced. It was fun, but rather silly, since RNG was even bigger than normal.
The idea I had just now is related to the upcoming tourney (1 attack creatures only, all other direct damage/weapons/shields banned except catapult) in some ways, but I think it's distinct enough to have its own theme.
Arthropods on a Plane!
http://en.wikipedia.org/wiki/Arthropod-The only damage sources allowed are arthropods. (deathstalker, forest scorpion, ?ash eater?, dragonfly, firefly, firefly queen, dune scorpion, ?devourer?, parasite, flesh spider, phase spider, ?chrysaora?, antlion, ?graboid/shrieker?, scarab, ?deja vu?, ?rustler?, plus any I missed) (?-? creatures are ones I'm not sure if they would count or not)
-weapons are banned (fight with insects, not swords!)
-shields are banned (too OP against mostly small creatures)
-all spells/permanents that deal damage to a player are banned (fight with insects, not spells!) (i.e. no bolts, nightmares, catapults, weapons, nymph's tears, unstable gas, boneyards, etc)
-no PC allowed except for butterfly effect
-CC is legal if it cannot be used on a player (rage pot, rain of fire, plague, dry spell, pandemonium, antimatter, reverse time, etc)
-firefly queen, fractal, and purify (due to all the scorpions) might cause problems, and they might have to be banned or partially restricted
-might have to watch whether nova, graboid, or quantum pillar would be OP or not as well
-you must have at least 6 cards that are a different element from everything else in the deck. (no monos or near-monos)
Ex. these are legal
A) 24 aether cards 6 gravity cards
B) 24 aether cards 3 life cards 3 light cards
C) 10 life cards 10 air cards 5 fire cards 5 water cards
D) 54 aether cards 1 entropy card 1 life card 4 water cards
E) 3 cards each from all 12 elements
Ex. these are illegal
A) 30 aether cards
B) 25 aether cards 3 water cards 2 life cards