I'm laughing over the Klingon/Ferengi mix. Actually, Ferengi + anything would be too weird. Here are some I'm imagining:
Ferengi/Bolian (practically just a blue blue Ferengi with a faint ridge down the centre)
Ferengi/Andorian (again a blue Ferengi with weird antenaes on the top of their bulbous heads and maybe a thin tuffs of white hair)
Ferengi/Cardasian (I have a very hard time imagining this, but I guess all those ridges plus big head and ears, maybe even some hair. Creepy)
Ferengi/Talaxian (big head, big ears, talaxian patterns on the side of their heads, hair forming a little "mohawk" down the centre
Ferengi/Vulcan or Romulan (BIG pointy ears lol)
Ferengi/Orion (a green ferengi)
Ferengi/Betazoid (its not really the funny factor but imagin the potential a telepathic Ferengi would have at the negotiation table! Yikes!)
Heheh.. so there you have it. Ferengi's should just stick with their own race.