Puyo Puyo is a puzzle game from Japan, and it has some great tunes. I don't know how to explain more without sounding obsessive to a concerning degree, but I'll try my best.
(Also, I don't know how to spoiler it on mobile, so bear with me here.)
Klug's theme, "Nebula Step" gives a sort of "cheery rock"(?) vibe. On my first listen it was odd, but on the next few listens it sounded pretty nice. The Puyo Puyo Chronicle version gives the original more energy and spirit, which is great. It sounds much better and fits the character, with or without the vocals.
Nebula Step (PPC, Instrumental)
Nebula Step (PPC, Vocal Track)
(There's also "I'm The Greatest Ever" from Puyo Puyo 15th Anniversary, but I haven't listened to it too much to form a solid opinion on it yet.)
I'm The Greatest Ever (PP15th)
Sig's (main?) theme, "Rapid Carefree Advice" fits it's name, being a very upbeat song to listen to. Personally the Puyo Puyo Chronicle version kind of.. ruins it? I'm not sure.. I just dislike it.
Rapid Carefree Advice (PP20th, Instrumental)
Rapid Carefree Advice (PPC, Vocal Track)
(I haven't listened to "In The Middle of Stroll" too much, but on first glance it sounds nice.)
In The Middle of Stroll (PP15th)
To move away from character themes, the Puyo Puyo theme is catchy and memorable, but my favorite version of this track is either Puyo Puyo 20th Anniversary's or the one from Puyo Puyo for the Genesis.
Comparison of All Puyo Puyo Themes (~PP20th)