Random musings of the blue and white Astromech…
It (he?) can climb climb stairs.
He can FLY!
He can plot a trajectory through hyperspace.
He can cattle-prod an intruder.
He can project a live hologram for conference calling.
He slices, he dices.
He repairs the vinyl trim on any car…
What other powers does this little guy have?
He can deactivate (or reactivate) any automated system just by turning some dial dealie.
He can fire a powerful magnetic towline strong enough to pull the welded head off another droid.
Band name!
Oh, nonononono…
We don’tneed anyone giving Andrew Lloyd Weber anymore ideas for bad musicals.
He’s a floorwax and a desert topping!
He also makes a groovy stashbox.
He can serve drinks pretty darned well, too.
And he’ll keep your beer cold.
He can pollish your shoes.
Condom dispencer.
piss poor home security alarm system, though (can’t even stop two huge poisonous milipedes from sneaking in a window through another droid)
He’s a blender.
Fixes hyperdrive systems.
Can be used to make cheap long distance calls.
Lawn mower.
Back/Wookie shaver/Flowbee (you know, the home hair cut device that sucks as it cuts)
Use as an emergency travel toilet? I think I’m gonna stop there.
He’s one hell of a hacker, too. He can override the security of any computer network and gain access to any data stored on it. Seems like nobody uses any firewall software in SciFi movies though. And everyone in the StarWars galaxy uses standardized data sockets & driod neck sockets. What, no SSL?
Let’s not forget his fire extinguisher. Or that he can come apart readily for easy stowage. And he has mag-locks on his wheels so he doesn’t fly off the hull of a starship. And he’s got more balls than any ten action heroes of the past five decades combined.
Plus, he doesn’t feel threatened by his best friend’s choice of an “alternate lifestyle.” 
Spring-loaded lightsaber ejector
Swamp monsters don’t like the way he tastes. That’s useful.
He’s waterproof, vacuumproof, and can resist any Yoda-sized attempt at theft.
He’s more expressive with whistles and beeps than most of the actors in the Star Wars movies are with English and facial expressions.
As anyone who ever watches the Man Show will notice, R2 has two very practical uses. The second use being a handy place to set your beer…