The first time I ever used a torpedo. It was around mission 6 or 7 in the SP campaign, and I had traded in my Javelin missile launcher which wasn't helping much anymore for a Starkiller launcher.
The first enemy ship I faced after that, we face head on, start shooting, I hit the torpedo button... <font size="+3">BOOM!</font>
Torpedoes have been my favorite weapon ever since.

(I've taken out three Bounty Hunter Hammerheads in one "jousting" pass with Tizonas and Sunslayers. Shoot-shoot-BOOM, shoot-shoot-BOOM, shoot-shoot-BOOM.)
Other "wow" moments were seeing the triple-sun Sigma system, the red-giant Omega system and limping over to Solarius station out of nanobots, seeing the pirate war system in Omega-5.
Oh, and another great moment was when I was entering New Tokyo system between missions in the SP campaign. While heading for the trade lane I scanned some adjacent ships to have something to do. One was full of Gold. I'd never pirated before and wanted to see how it works. Started shooting the transport, and the instant it exploded I hit B and jumped into the trade lane. Didn't even see what I'd picked up until I landed on New Tokyo, but it was 30 units of gold and I was suddenly $40,000 richer.