I made a post a while back saying I was worried that the MSF class wouldn't have a bike big enough to fit me, and I'm happy to say it turned out they did. Well, almost big enough. I rode a Nighthawk, which was the biggest bike they had. I bumped the handlebars against my knees during the slow, tight figure-eight exercise, but aside from that my size didn't present any problem. I passed the class. Thanks to everyone who posted on that thread.
So now I'm looking for my first bike. I'm pretty sure I'll get a cruiser, but that's not set in stone. Could anyone recommend some cruisers that'd be good for a 6'5", 250-pound guy who's just starting? By the way, I'm 21, but please don't let my youth deter you from recommending a more powerful bike; I'm as cautious and responsible in a car as any 40-year-old, and I'll be the same way on a motorcycle. If there's a bike you wouldn't recommend simply because it's unsuitable for any beginner, that's fine, but please don't leave a bike off the list because you think its power might tempt me to be reckless. I'm a cautious rider/driver, really.
I don't have a cruiser recommendation for you (don't ride 'em much), but I did want to point out something about the second part of your post.
The caution about getting an excessively powerful bike as your first ride is not about age, or whether you are responsible. A lot of people take this way too personally. We don't think you will be reckless. The reality is that, as a new rider, you will be making some mistakes. If you make those mistakes on a forgiving motorcycle, you stand a better chance of surviving the learning curve. I posted somewhere else that, at the airport, we rarely (ok, NEVER) send student pilots up in Lear jets. Same principle.
Some typical mistakes I've seen over the years (and read about here as well) involve mismanagement of the throttle or brakes when something unusual happens. The more managable your 1st bike is to begin with, the more likely that mistake will leave you with the wheels on the ground.
A couple of noob scenarios I've seen recently :
Sportbike noob doing about 30 mph approaching a red light. Car starts to pull out of a parking lot in front of him, but sees him at the last minute and stops short. Noob saw the car pulling out and grabbed a handful of highly responsive brake and launches himself right over the bars of his brand new ZX-6. Simple beginner mistake, but if he'd been on a tamer bike, he probably wouldn't have been able to pull that manuever.
Last week, sitting in traffic at a light about 2 cars back and to the right of a leather clad noob on a very large Honda cruiser (1800 I think). Light turns green and he accidentally stalled it. Horns start honking and the guy gets in a hurry. Started it. As it was still revving from the fast start, he lets the clutch out a little to fast. I watched his upper body snap back horizontally, as his bike launched itself, out of control, into the intersection as he looked at the sky. Fortunately, it tipped over before he hit anything. Had this guy NOT had over 100 ft./lbs. of torque hitting his rear tire at a mere 3000 rpm, he probably would not have dumped it in a busy intersection.
BTW - The reason I know so much about these incidents is that I was the guy who help them scrape their new rides off the pavement. I seem to get that opportunity every few months these days.
As for bike recommendations. Yamaha v-star 650, Honda shadow VLX, Suzuki Boulevard S50, C50, or M50, Kawi Vulcan 500 or 750, HD sportster 883. Those are all pretty decent smaller cruisers, big enough to be comfortable for a big guy but with more managable weight and power level. And all of them except the vulcan 500 are v-twin powered
The Buell Blast is a very decent learning machine, I have one and tiped it over twice, but its hardly took any damage at all (under 50$ worth) and I escaped with releativly minor scrapes and bruises, and now I can do some stuff decently even though I definitly need to work on some stuff.