Hearthpwn

Patches the Pirate

Sir Finley Mrrgglton

Babbling Book

Small-Time Buccaneer (Pre-nerf)

Arcane Artificer

Mana Wyrm

Swashburglar

Tunnel Trogg

Zombie Chow

Fire Fly

Righteous Protector

 Undertaker (Pre-nerf)

Mistress of Mixtures

Kobold Librarian

Troggs rule! Fist!

Pavel votes for Babbling Book obviously.

Where's Northshire Cleric?

Patches WAS the best, for obvious reasons.

Swashburglar WAS good, because it enabled patches. still decent tho.

I like firefly, really well balanced value.

Where is Northshire cleric???

Mistress of Mixtures not being on this list is weird. I think she's the 3rd best after Mana Wyrm and Patches the Pirate.

Tunnel Trogg was good for his time, but he's just okay now. He can't get out of control anywhere near as easily as Mana Wyrm.

Where are pre-nerf Undertaker and Small-Time Buccaneer?

Ever? Undertaker before nerf :P

Pre-nerf Patches. When a card makes Bloodsail Corsair a good tempo play in any class, you know it's busted.

Pre nerf undertaker lol.

This is the issue: Does you mean what is the strongest minion right now or ever?

Right now in all formats: Northshire Cleric
In all time of Hearthstone: Undertaker (naturally pre-nerf)

Undertaker Hunter had the highest winrate a deck in Hearthstone ever had; was quite good in Naxxramas, but in GvG it was so insane with the addition of Piloted Shredder, that the nerf was necessary.

best designed/most interesting/most versatle goes to cleric and fire fly.

broken/stupid/OP goes to patches, trogg, wyrm (i wasn't around for undertaker hunter)

Patches clearly before the nerf (Undertake even more so), but right now it's Mana Wyrm.... but it kinda has to be since mage minions are weak overall.  Northshire may be well-designed but it should certainly be on the list.  Fire Fly being neutral makes it OP in the sense it's good in any deck and any class can use it, but certainly doesn't break any games.

Fuck Patches.  Mana Wyrm and Tunnel Trogg if left unchecked snowball quickly.  Undertaker was a cheating card though, way too op for a rare. The fact that patches is a legendary means it should be op, but the others are commons and rates and still dominate 

I had to go to the Undertaker's page for his 'Oh, goody ♫" attack cry. Oh how I missed that!

Well.. Angry Chicken

In nowadays HS? Finley! He can give you sooooo much power!

As an all time icon? Undertaker...

My top:
1. Undertaker (Pre-nerf)
2. Tunnel Trogg
3. Patches the Pirate
4. Sir Finley Mrrgglton