USS Defiant NCC-74205
The USS Defiant was the first of it's class, a combat prototype created specifically as a weapon to fight the Borg. However, the project had been mothballed. In 2371, the ship was brought into active service by Captain Sisko to help defend Deep Space Nine and the Federation from the Dominion threat. Since then, it has played a key role in the Dominion threat and in defending the Federation against the second and third Borg incursions to Sector 001 (Star Trek First Contact and Season 3 episode "Lonesome Road").
I admit, I never really watched Deep Space Nine. I really liked the last season, but before then, the show never really caught my attention. However, I did see quite a few episodes, and the Defiant has made a couple of appearances in Star Trek Dragon. It's a fun little ship, in my opinion :)