Portal is a first person puzzle platformer created by Valve that cost $9.99.
Even though the only organic sentient being in this game is the player's character, this game features some of the most memorable and intriguing characters in fiction or in gameplay. GladOS obviously, but also the drone robots that sweet-talk the player to a sudden death (and then forgive you when you dismantle them), the clues left behind by former test subjects, the abandoned hints of what the lab used to be like. It tells a story without telling a story, and immerses you more than most other games can ever hope to achieve.
Pro Merges first-person shooting mechanics with platforming and puzzle-solving
Portal uses an engine that was meant for a first person shooter and creates puzzles that need solved through various stage with the use of platforming. While not the very first game to merge platforming with and FPS the puzzle aspects make it unique in that no other game had done this specific combination yet.
Pro Created one of the most memorable characters in gaming history - GLaDOS
GLaDOS, or Genetic Lifeform and Disk Operating System, is the main antagonist of Portal games. She is voiced by Ellen McLain with the voice later processed to sound closer to how a text-to-speech program would synthesize a voice.
GLaDOS initially functions as a guide to the player and is only later revealed as a manipulative, narcissistic, sinister and passive-aggressive character that wants to kill the protagonist.
GLaDOS is the main force that moves the humorous yet dark narrative of Portal series with her remarks being simultaneously hilarious and terrifying.
Con Portal mechanics not used much to their best ability
Certain parts of the game sees the player using portals to manipulate sentry guns that fire rockets in order to progress in that stage, Mechanics like this make for a really enjoyable way to manipulate ones environment but sadly are not used too often.