Alien Attack by Terry Roper is a pretty neat side scrolling action game for the Commodore 128 in 40 column mode.

Battle Blox by Hydrophilic (2007) is a Tertris like game but instead of interlocking shapes, you match colors.  The neat thing about this game is you can play against another human player.  Full source code is included in the archive.

Block Drop 128 is a Tetris like game for the Commodore 128 (80 Columns)

Boulderdash 128 by Pyrofer (2016) - Here is an excellent example of a Commodore 128 action game in 80 column mode.  It didn't work in VICE for me, but some say it does.  I used Z64K and it worked great.

Here's ia thread on the Lemon64 Forum where you can find some more detail.

Also, here is a link to a really interesting interview with the creator of the original Boulderdash.

Cross Bomber by Fabrizio Caruso is an 80 column mode game for the Commodore 128, developed with the CROSS-LIB framework.

The game's goal is to destroy all buildings so that you can land on an empty road. The game is a clone of Air Attack (aka Blitz) game that was first developed on the Commodore Pet. The game is controlled by the single fire button (first joystick button for targets with joystick input and space key for targets with keyboard input). Your score depends on the number of building destroyed, the level reached and how fast you complete each single level. The game has 8 levels and it ends after the eighth level.

Cross Chase by Fabrizio Caruso is an action game for the Commodore 128 built with the CROSS-LIB framework.  This game comes in four versions; 40 & 80 column versions for the 8510 cpu and 40 & 80 column versions for the z80 cpu.  All four versions are in the archive.

The game's goal is to lure the "ghosts" into the mines and possibly kill the "skull" by repeatedly using the gun. You have to avoid all enemies, the mines, all walls, rockets and chasing missiles. All flashing items have positive effects and can grant you some special powers. Discover the 10 items. If you use the gun against the skull and/or the missiles and rockets, you can unlock some special secret items. There are 20 different levels including 4 boss levels.

Crush is a game for the Commodore 128 (40 column mode) written in BASIC that falls into the "breakout" type of genre with horizontal play.

Dropzone by Arena Graphics is a defender like game for the Commodore 128 (40 Columns).

Frantic Freddie II for the Commodore 128 (40 Columns) is a game in which you collect the pots of gold resting on the platforms, as well as optional bonus items which scroll through the playing area by navigating telegraph poles to get to the various platforms.

Note - Requires Z64K Emulator or a real C128

Ghost by Elwood Software is a simple game for the Commodore 128 where you must defend a monastery from ghosts.

Invasion 3:Astra by Chris Batchelor and Echo Magnetic Media is another Commodore 128 - 80 column game released in 1992.

KISS 128 for the Commodore 128 (40 Columns) is a party game almost certainly written by a teenager.  The idea is to get 10 to 20 males / females and randomly have them kiss each other on various parts of the body.  NOT X-Rated.

Note:  Use Dload to get this running instead of normal Load

Maggot by Peter Karlsson is a mini game for the Commodore 128 (40 column mode) released for the Minigame 2002 Compo.

You are a worm (or maggot, in this case), and your aim is to eat as many targets as possible. Whenever you eat a target, the worm grows. If you run into the walls or yourself, the game is over.  The game is controlled with the numbers on the numerical keypad: 8 for up, 4 for left, 6 for right and 2 for down. Any other key makes the worm stop, which means instant Game Over!

Welcone to Mikes Maze! Random mazes will be drawn on the screen. A black dot will appear in the lower right corner of the screen. With a joystick in port two your goal 1s to get to the top of the screen without touching the sides. If you touch the sides you will be sent back to the beginning. The left side wraps around to the right, good luck!

Millifoot 80 by L.K. Snyder, released in 1988.  This action game for the Commodore 128 is an 80 column clone of the classic Atari game called Centipede.

Quick Eyes 128 v1.2 (5-7-2008) - This is a simple but fun game for the Commodore 128 in which you have to see how fast you can spot the correct number of colored squares on the screen.  

The object of the game is to guide a green duck through eighty levels. Fruit and gems can be collected for points, and enemies are eliminated with projectile egg weapons. Progress through the game is earned by collecting gold and silver keys. There are a variety of power-ups also available, including 'chocolate egg' weapons and extra shots.

Space Hit 128 for the Commodore 128 (80 Columns) is an action game in which you have to dodge asteroids with your space ship.  

A prototype version of Tempest for the Commodore 128 (40 Columns) - Runs very very slow but warp mode in VICE helps.