Ok, I'll bite...
The stock 3-speed is a really solid manual transmission. And a real good choice if that is your only requirement.
Beyond that the sky is the limit. What's your budget? Do you want an overdrive? Do you have the correct axle gearing for the tire size you are running? Trick question, correct axle gearing will also depend on if the transmission you pick has an overdrive and what the overdrive ratios is. Highway driving? If so what kind of highway driving?
LAst time I checked there was a decent list of transmissions in the tech section on the left side of this page.
Do you want a truck like transmission, or a car like transmission? Do you know the differences? How will the Bronco be used? I could keep asking questions for the next half hour but have other things I need to be doing right now.