So far my favourite is rogue. This game is custom made for pack-rats and hoarders. Rogues can steal all the things. And mine does.
For a similar reason, bards come in a close second. My bard and Astarian have been tag-teaming their way across Faerun abusing perform and pickpocketing. Where the bard excels is in exploring all the dialogue and roleplaying choices.
Next come cleric, druid and paladin. They are all pretty much tied. I have found barbarian, fighter, wizard and sorcerer to be a bit bland.
I have not played rangers and warlocks. Rangers because I haven't gotten to them yet and warlocks for reasons (Wyll).