I know I'd never get to make out with her without dying, but I choose Poison Ivy. At least she has decent intentions and occasionally does the right thing, and as long as I'm eating organic and recycling she probably won't kill me.
when I first saw the question I immediately started thinking Catwoman..and she's still my first pick even though when I think about it I've got better odds of getting castrated by her because I keep hitting on her/trying to flirt with her than I do of actually wooing her and getting laid....that said though since she's ultimately not a choice on the poll I think I'll go with Riddler mainly because I consider myself to be close enough to his level of intellect that he'd deem me worthy of working for him and not in the thug on the street sort of way.
Id team up with the riddle, A) I rekon I could take him in a fight. B) hes ginger and I could vent the accumulated jokes I have collected from having a ginger sister.
and all things aside I think other than the joker hes my favourite, Id work for the joker but hed kill me just for lols and that would be sucky.
Of those? Penguin is rich, so I'd actually have a chance of getting paid, and he's not an out-and-out psychotic in most incarnations, so I'd have a better chance of not getting whimsically killed off, and most of his crimes are about money rather than proving he's smarter than that black-bedecked-bat-brain or love of chaos or hatred of humanity or (etc. etc. etc.) so there's a much greater chance I'd continue to get paid rather than getting sacrificed for my boss's cause.
Of course, first time something goes really wrong on a mission someone's going to take the fall, but I think that's pretty much the case with any of 'em. Mission goes south? Time to leave town.
Even trought Ra's Al Ghul is my favorite Batman Villain i would go for the Penguin... He is pretty much a business man. I think i have least chance to get killed or somehow screwed with him than the others