Railroad Rampage

Free, 2D graphics, http://neotron-games.blogspot.com/2009/10/railroad-rampage.html

In this Tower Defence variant, bandits attack your train to steal the entire freight. Your task is to construct special turrets to defend the cars as long as possible.

OpenLieroX

Free, 2D graphics, http://www.openlierox.net

Players alternately take charge of an army of worms that are armed to the teeth in an unfriendly terrain. As in the game Worms, the surviving team wins.

Puzzles

Simon Tatham's Portable Puzzle Collection

MIT license, 2D graphics, http://www.chiark.greenend.org.uk/~sgtatham/puzzles

A good puzzle solver will find his collection rewarding. A number of good examples await.

Connectagramm

Free, 2D graphics, http://gottcode.org/connectagram

Connectagramm provides an interesting variation on the old crossword puzzle. The game starts with a few scrambled words that need to be unscrambled. The dictionary is customizable and, in the reviewers case, located in /usr/local/share/connectagramm/words. You can add or delete words, to form a non-English version if need be.

JAG

Free, 2D graphics, http://jag.xlabsoft.com

The puzzle game is a rather bold yet attractively presented BeJewled clone in which you swap objects in adjacent tiles. If three or more of the same object are in a row, they disappear. The idea is to remove as many objects as possible.

Tanglet

Free, 2D graphics, http://gottcode.org/tanglet

In this electronic version of Boggle, the player has to assemble as many words out of the 4x4 grid of characters, horizontally, vertically, or diagonally, as she can before the time runs out.

Rocks'n'Diamonds

Free, 2D graphics, http://www.artsoft.org/rocksndiamonds

The puzzler and strategy game rejuvenates the good old Boulder Dash on the PC. As a prospector, you tunnel for diamonds. Watch out for rocks, though, in that they can tumble in on bad tunneling work.

Wizznic

GPLv3, 2D graphics, http://sourceforge.net/projects/wizznic

Wizznic brings a combination of Tetris and Sokoban to the screen. You shift small blocks with imprinted symbols around a maze, if two meet, they disappear. The goal is to empty the maze.

Bricks 3

Free, 2D graphics, http://sourceforge.net/projects/bricks3

This simple Tetris clone has blocks of varying shapes fall into a cup. If three of the same touch, they disappear and your point factor goes up.

BrisKola

Free, 2D graphics, http://www.briskola.net

A visually appealing version of the popular Italian card game.

Hotei's Jewels: Relax

Free, activated 3D graphics, http://www.wegroup.org/games/puzzle-logic/hoteis-jewels-relax.html

An enlarged BeJeweld clone. On a board game, place identical pieces next to each other by swapping.

Zaz

GPL, activated 3D graphics, https://sourceforge.net/projects/zaz

Colorful balls come rolling down a long, snaky chute. Swapping balls to bring the same colored ones next to each other takes them out of line.

FreeDoko

GPL, 2D graphics, http://free-doko.sourceforge.net/de/FreeDoko.html

Visually appealing card game for multiple players.

Tubularix

Free, 2D graphics, http://tubularix.sourceforge.net

A kind of three-dimensional Tetris. Groups of blocks drop along the walls to the bottom of a funnel. Each successful placement raises the score.

CuteMaze

Free, 2D graphics, http://gottcode.org/cutemaze

The player takes his character through a randomly generated maze. The game ends once all scattered targets are picked up.