Blissey weak to fight moves. When facing P/HB Blissey, Machamp is a given.
Due to recent advice seen on another question, I looked up fighting quick moves, and who has them. Doing this I saw that, even though not Fight type, if the pokemon's attack is high, then the move does greater damage than one with STAB (according to the ranking of damage given for the move).
So, with that, I looked at the pokemon with high Attack, and the fighting quick moves, with a high powered charged move w/stab, vice versa, or combo fighting movesets. And found that these are highly useful in beating Blisseys, especially when Machamp isn't available, or a mon that's more ZH/DG, ZH/P, resistant is needed.
This is a list of pokemon, outside of pure fighting types, that have a high base attack with combo fight moveset, or fight moves combined with a STAB move, that are good against the "feared" Blissey.
Pokemon [base attack]-(moveset)
Alakazam [271]-(psycho cut/focus blast) or (confusion/focus blast)
Gengar [261]-(hex/focus blast)
Pinsir [238]-(rock smash/close combat) or (bug bite/close combat)
Ursaring [236]-(counter/close combat) or (metal claw/close combat) or (counter/hyper beam)
Rhydon [222]-(rock smash/earthquake) or (rock smash/stone edge)
Kabutops [220]-(rock smash/stone edge)
Donphan [214]-(counter/earthquake)
Granbull [212]-(bite/close combat)
Ampharos [211]-(charge beam/focus blast)
Rapidash [207]-(low kick/fire blast)
Magmar [206]-(karate chop/fire blast)
Electabuzz [198]-(low kick/thunder)
Poliwrath [182]-(rock smash/dynamic punch) or (rock smash/hydro pump) or (bubble/dynamic punch
Might have left some out, some of them are obvious, but this should help someone out there who hates Blissey because they think they are too hard to beat, and need to be nurfed. Also, a see a lot of complaints about movesets, there is always a use for them. I have also tried some of these against Blissey, and I was surprised with Rapidash. It fainted, even with dodging charged attacks (duh), but got Blissey down far enough to get knocked out with one charged move from my next pokemon. Hope this helps.