
1123 - TOS - S2 - 5/5 - 2x17 - A Piece Of The Action
TOS - 2x06 - The Doomsday Machine
The Enterprise discovers a superweapon capable of destroying entire planets, and a Commodore whose crew was killed by the machine jeopardizes the crew on a crazed mission of revenge.
http://memory-alpha.org/en/wiki/The_Doomsday_Machine
TOS - 2x08 - I, Mudd
Harry Mudd, now ruler of a planet of androids, captures the Enterprise and attempts to imprison Kirk for revenge.
http://memory-alpha.org/en/wiki/I%2C_Mudd
TOS - 2x13 - Obsession
A survey of Argus X brings the Enterprise crew in confrontation with a vampiric cloud that killed a crew Kirk was on years ago, captained by the father of an ensign currently assigned to the ship.
http://memory-alpha.org/en/wiki/Obsession
TOS - 2x16 - The Gamesters Of Triskelion
Kirk, Uhura and Chekov are kidnapped to fight each other and other aliens so gamesters can bet on the results.
http://memory-alpha.org/en/wiki/The_Gam ... Triskelion
TOS - 2x17 - A Piece Of The Action
Returning to a planet last visited by a Starfleet ship 100 years ago, the Enterprise finds a planet that has based its culture on the gangsters of Earth's 1920s.
http://memory-alpha.org/en/wiki/A_Piece_of_the_Action