The "Theme From Red Dwarf". It segues from your ordinary sci-fi spaced-out theme to the most over-the-top rock and roll craziness imaginable. Pity the full thing was rarely shown on the show.
"Tongue-tied" manages to be Music of Awesome and Crowning music of Funny! And, wow, can John-Jules strut!
The episode "Gunmen of the Apocalypse" gives the theme tune a western spin, resulting in one of the best and most spine-tinglingly awesome pieces in the history of Red Dwarf. The Western music plays whenever the Dwarfers are being badass and also at their Moment of Awesome at the end.
From "Queeg": There's a brief rendition of "Do Not Forsake Me, Oh My Darling", sung by Howard Goodall (who sang the chorus of the Rimmer Song and composed the theme tune) as Holly prepares for his showdown with the title character. It's only short, but it's incredibly well done. Here it is in all its glory.