Geez, you people have very selfish Blisseys. Here's mine:

Blissey (F) @ Leftovers
Ability: Natural Cure
EVs: 200 HP / 176 SpA / 132 SpD
Calm Nature (+SDef, -Atk)
- Ice Beam
- Thunderbolt
- Wish
- Heal Bell
Basically, this is a Cleric Bliss, which got an upgrade going into Gen V. Wish in Gen V now heals 50% of the user's HP, even when switching to another Pokemon, on this Blissey, that is 350 HP; enough to fully heal just about anything on an average team. So the idea for this Bliss is to switch into a Spec attacker, and Wish on the likely switch. Heal Bell is one of my favourite moves, especially with the influx of Toxic users, Will-o-Wisp, and Thunder Wave ferro. The Bolt-Beam combo works well for Blissey, as a lot of Special attackers are Water, Dragon, or Grass types, and it hits a few more that aren't.
EVs give it 701 HP (enough to take 8 Seismic Tosses, and heal 350 HP), 230 SpAtk, and 372 SpDef. Natural Cure is the best ability on Bliss, if someone tries to use Toxic, or put Blissey to sleep, just switch in a new Pokemon, problem solved, and Bliss is good to go again.
Here is a Chansey variation of the same set:

Chansey (F) @ Eviolite
Ability: Natural Cure
EVs: 240 HP / 248 Def / 16 SpD / 4 Spe
Bold Nature (+Def, -Atk)
- Seismic Toss
- Toxic
- Heal Bell
- Wish
Possibly a better set, it has the same Cleric base, same HP, but a higher defenses and a more stall-like approach to offense. Seismic Toss will always do 100 damage (at level 100), and Toxic will kill the opponent slowly, or force a switch for you to Wish.
The Eviolite give Chansey 375 SpDef, and 217 Def (Blissey's is 56, 130 Max), and it still has 701 HP, it can take hits all day, and is actually better than Blissey in most cases. I throw 4 Speed on the EVs mainly as filler, but also so it won't speed tie with other Chanseys, this thing is popular.