Here is a list of games in Minecraft I have thought of.

MINECRAFT TAG:
The rules are slightly tweaked:
If you want to play, teleport to the person who announced it. When all of the people are there, the game starts (obviously). The person who has their username highest on the username list in alphabetical order is "it." He faces the ground or a wall, and counts to a specific number everyone votes for.
When a person is tagged, he/she is it.
No hacking, cheating or teleporting allowed.

DOUBLE SPLEEF:
Rules:
It's similar to spleef, but the play area is double floored.
You start on the first floor, which is the same as usual, you play normally, but when you drop down, you end up in a maze. Unless you land on a wall of the maze. You navigate through the maze, finding your way to a staircase. When you meet someone on the way, you are allowed to delete the blocks under them, as usual. The staircase leads back up to the first floor. If you fall on the second floor, you lose, and fall into a pit (usually filled with a liquid) and there is an exit.
Obviously, there will be observation areas.
Unlike the regular spleef, there may be up to eight players.

MAZZ:
Rules:
It's sort of like a cross between mazes and obstacle courses.
The whole thing can be as big as it wants, only if it's over 30x30x30. The pathways in the maze can be as big as it wants, only if it's bigger than 5x5x5. The pathways have to fit an obstacle course.
There can be multiple floors. Each dead end is a hole that leads to a lower level, or even out of the mazz.
There are races allowed, but it's optional.
The person/people are allowed in the "owners" area. It's just a connection from the start to end, covered with a glass door. Their job is to keep track of who finishes first/second/third/ect, and keep track of the players in the mazz and allow access.
NOTE: No idea where the name "Mazz" came from, it was a random thought.

UMMWAT'S CONTEST:
Info:
It's basically a Minecraft Olympics sort of thing. It will be on some winter breaks/summer breaks. I will keep track of all players and points. Some get you zero. Some get you one hundred.
I will not do this EVERY year, but I will announce when I will, which is when I feel like it.
I will post a thread containing all info on it.
There will be a closing ceremony (I will change one section of the map to a party style, and delete when done).
On 4:00 PT (Pacific Time), the event will start.
I will cancel when things don't go as planned.
Registering will start on the day before it starts on the thread.
THIS ENTIRE THING HAS A VERY TINY CHANCE OF HAPPENING (if allowed).

You may post your own games that you have come up with here, or another thread/topic/whatever you call it.

List of all games:

Spleef (?)
Chess (?)
Stump (Obstacle Course) (?)
Maze (?)
Double Spleef (ummwat)
Mazz (ummwat)
Hoops (SYNTAX_ERROR)
Tic Tac Toe (?)
Checkers (?)
Theatre (dunk443?)
Survival Arena (?)
Pits (Nutnoze)
Tag (?)
Hide and Seek (?)
All Other Tag-Related Games (?)