Heres my list of suggested gamemodes.
1. Flood [ Water will rise slowly and once you touch it you die you have only one life.]
2.Acid Rain [ Randomly fakekills bricks from the sky and if you get hit by it it removes a body part/kills you]
3.Tsunami [You place a brick like against a wall and it shoots out projectiles which are huge bricks [Water bricks] on touch they kill you.
Things about them
Tsunami : Best used in enclosed area.
Flood : Brick count of 150 then your screwed.