Gen 1- Blastoise, my first water starter that has made me pick water first in all games since then, also it's mega evolution has a howitzer on it's back
Gen 2- Skarmory, There are two things I love in Pokemon, steel types and unique typing combinations, Skarmory has both by being the only steel flying type allowing it to soar safely above any jackass with earthquake that would normally ruin a steel type
Gen 3- Gardevoir, picking my favorite from gen 3 was incredibly difficult with pokemon like Metagross, Swampert, Blasakin, and Argon all among my favorites in this gen. But it was the addition of fairy typing to Gardevoir in gen 6 that put her ahead for me and made her my favorite from Hoen
Gen 4-Lucario, I find Lucario to be a very interesting steel type since it is based more on attack, special attack, and speed rather than defense so it can use any number of the powerful steel type attacks to their full potential, also having a fighting type with a decent special attack is very interesting
Gen 5- Krookadile, The first time I used a dark type and he passed the test with flying colors, being incredibly fast and powerful made him a beast of a sweeper along with the ability moxie that upped his attack every time he got a kill. Being part ground also came in handy quite often
Gen 6- Aegislash, My overall favorite pokemon was one I knew I was going to pick up upon first hearing about it, it's a god-damn sword that has the unique steel/ghost typing, sign me up. However it wasn't until after I had evolved my honedge all the way to Aegislash that I learned of its power of stance change which would cause Aegislash to change into shield mode or sword mode based on what move you used and would transfer 100 points to your defence or attack stats respectively.