Ultimate Fighters has a huge soundtrack, and the songs are listed here:
Claus/Goomy the Mighty's Theme: https://www.youtube.com/watch?v=lHEhkeRlldQ (Natural Killer Cyborg Theme from Mother 3
Matthew's Theme: https://www.youtube.com/watch?v=DVcyZ_TtLhI (Sanctuary Guardian Battle theme from Earthbound)
Dwid's theme (placeholder): https://www.youtube.com/watch?v=XnJwd9zrjiA (Elite Four Battle Theme from Pokémon B/W)
Sonic's theme: https://www.youtube.com/watch?v=HjEQq2x-6yQ (Green Hill Zone theme from Sonic Generations)
Mario's theme: https://www.youtube.com/watch?v=cgRP-F-TOOo (Super Mario Bros. Overworld theme, Super Mario All-Stars)
Gir's theme: TBA
Zorua's theme: https://www.youtube.com/watch?v=iDFEUfS4r_A (Champion theme, Pokémon HG/SS)
Edd's theme: TBA
Thomas's theme: TBA
Matt's theme: TBA
Espurr's theme: https://www.youtube.com/watch?v=2O7MmZ8geMw (Old Chateau theme, Pokémon D/P/PT