Gangbangs are a top fetish of mine (really anything involving a lot of cum), human or animal, both watching a partner and also being on the receiving end. Of course being one of the guys doing the banging is great too, but I mostly am turned on by the idea of watching a gf/wife being gangbanged or getting gangbanged myself.
Particularly with the watching a gf/wife thing, it would just be so hot watching her be so slutty and getting filled and covered in cum getting so much pleasure. The real kicker would be after all the others were finished it would be my turn and I could kiss her cum covered mouth and face, lick her cum filled holes, and then pound the fuck out of her with all that cum as lube. It's not a cuckold type thing, which a lot of people view it as it seems, it's just really hot. But... it is imperative, except for limited circumstances, that I get to go last and have my way. Hence part of why I say it's not about any cuck type thing.
Actually, it would be even better if we are both getting gangbanged at the same time. I'd be over the top horny watching her while I'm getting fucked and filled with cum at the same time. Preferably some of the guys fucking her would hold back cumming and then switch to me using my gf/wife's dripping pussy juice (assuming they are a cis woman in this circumstance) and the other guys' cum to slide in me nice and slippery.
With dogs it's pretty much the same thing. Even with just one dog I'd have a hard time NOT getting the sloppy seconds, or drinking the big load of dog cum out of her before eating her pussy and ass till she cums. Ideally I could be under her in a 69 as she takes on a group of dogs while she is sucking my cock. I don't know how long I could last before exploding cum in her mouth/down her throat though lol. Of course again, if we could both be getting gangbanged by the group of dogs at the same time that would be great... And then we could fuck each other after!