Games
Barrack
Ambrosia Software has not created an OS X version of this terrific game, unfortunately. When I was using OS 9, I played it frequently, eventually scoring 3.4 million points and getting to level 76.
Flash Fabrica
Here are the instructions for this interesting game/test. Don’t worry about the time it takes you to position the cursor in the circles corresponding to the numbers flashed before you. Just concentrate on the positions of the numbers flashed on the screen. You may be more comfortable using your mouse than the track pad.
1. Click on START.
2. Wait for 3, 2, 1 (number of seconds you have to prepare yourself mentally).
3. Make note of each number’s position on the screen and then click the circle for the SMALLEST number to the BIGGEST number.
4. At the end of the game, the computer will tell you the age of your brain.
* * *
Decided to try this again; here’s the score I received today (15 February 2009):

Bookworm
Bookworm is a mind-strengthening game and a vocabulary builder, to use the popular term. One irksome thing about it is that it does not give definitions for many words, and some of the definitions it does provide are less than satisfactory. For example, it refers to poi as a food of the Hawaiian nation, and the word rut is defined in a narrow way–and not the way most of us use it. There are also typos and other kinds of errors in some of the definitions. I have occasionally found a few unsavory words in the game, so be prepared for those to come up. My highest Bookworm score to date is 6,643,970 points, and the two words that I scored the most points with were sovereignty (24,120) and fleeced (17,400).
I started playing a new game this year and have reached 6,411,020. One thing that is making this game difficult is the large number of unusable letters in the bottom half of the board. High-scoring words in this game are quavers (18,300) and rollings (20,060).

plobb!

Image from Nothing from Space, creator of plobb!
My friend Alex told me about this game, listed as a “staff pick” at the Apple website. I’m guessing that I’ve played it several hundred times, achieving my top score on 5 May 2009: 516,355.
plobb, we’re told, is being kept in the dungeon of the Evil Motts of Psodor. Our goal as plobb’s liberators is to pop, using a delightful array of weapons, the bubbles of depression that keep him imprisoned. After twenty-five rounds of bubble popping, we meet Motts himself.
Samorost 2

Image from Amanita Design's site.
Luckily for us, Amanita Design’s award-winning game is free in its simpler version and less than ten dollars in its complete version.