The first musical of their's that I saw was Pac-Man the Musical: A Pacapella Song. Which as a fan of the old arcade machines this peaked my interest in what they did (I am still terrible at Pac-Man however).
One thing they do that makes them unique is the fact that they do what they call "Bonus Encounters" which are generally short behind-the-scenes, additional little musicals, skits, or just odd little tidbits, here is Pac-Man musical temp track which was shown to the cast before recording.
RandomEncounters preformed one of their most popular musicals Needlemouse: The Musical at Sega's Sonic Boom at E3. Sega is the publisher of the Sonic the Hedgehog games that Needlemouse is based on. If the actual company recognizes the song as good advertising without having to do any work themselves than we know that we have something.
Check out their others musicals such as:
- The Legend of Ganondorf: A Zelda Song
- Singachu: A Pikachu Song
- Angry Birds The Musical: A Green Pig Song ("When I take flight my pigging sprees" is forever stuck in my head)
- Nicole: A Dead Space Song (Dead Space: The Musical)
- Nothing Is True: An Assassins Creed Song
Check them out, they're pretty good and just keep getting better.