I've successfully de-gunked many devices with vinegar (I use the apple cider variety since that's what I keep around for other uses, but any kind works)... graphing calculator, several remote controls, small clock, emergency radio, headlamp, probably some others I'm forgetting... I usually just wipe a little vinegar on the problem areas with a q-tip and/or small piece of paper towel, not drenching it, and haven't noticed any harm to the rest of the contact points and interior that way. The stubborn bits of gunk in tight areas sometimes need a little help with a small pick or knife (sometimes need the knife to pry out the batteries in the first place too; I use a butter knife to avoid unnecessary gouging).
Most of my leakers have been Duracell (even some unused, still in the package!!), though there's been a few Energizer too. I have contacted Duracell before when I actually caught a leaker before the batteries' date was passed. They made me read off some tiny barely-legible code numbers embossed on the side of the batteries (so don't toss them out right away if you plan on calling - and have a magnifying glass and bright lighting handy when you do), and sent me a coupon good on a replacement pack of batteries (enough to pay for a much larger pack than the batteries originated from). Unfortunately some of that replacement pack ended up leaking too.
Lately I'm focusing on basic Rayovac alkalines. They have better prices and work just as well, with what seems to be less propensity for leaking these days than the bigger brands. I've found them at Walmart, Kohl's, Home Depot, and Lowes.
Rechargeable NIMH are definitely safe, but then you have the ongoing hassle of charging/rotating (even the low-self-discharging ones will eventually discharge to the point of no return if you forget them too long), and if you try using them in everything, you might find some of your devices aren't okay with the slight differences in how they put out voltage compared to non-rechargeables.
The other thing I'd recommend if you can afford it are Energizer primary (non-rechargeable) lithium AA/AAA. Energizer unfortunately has a monopoly on this type of AA/AAA battery in the US, so they are not cheap compared to other batteries, but they are virtually leakproof just like the primary lithium button batteries are - great thing to leave in less-used devices that you want to be sure will work when you need them.
PS: All my leak problems so far have been with AA/AAA and 9V (which have tiny AAAAs inside them). I've had much better luck with C and D batteries of all brands and off-brands not leaking, even long past their dates. Obviously it can happen with those too, as the 4D Maglite guy shows, but I think their larger size maybe provides more room for better sealing/separation inside.
