What's it called?

The bulb popped in the lamp today when I turned it on as dusk drew in so I had to scuttle across the road to the local Billa supermarket to get a replacement bulb before they closed, or spend the whole night in gloom and flicker form the TV and the laptops.

I took the blown bulb with me to ensure I was bought the right replacement but also as I realised that I hadn't the foggiest idea what the german was for light bulb, if I had to ask one of the shop assistants for one. In the worse-case scenario I figured I could at least prod it and say "I would like one of these please my good man" point point.

As things turned out, I found them on the shelves quite easily but decided to seize the day at the till by asking the cashier what they were called. By this point, the only possibility that had found its way into my head was Lichtkugel (der, die oder das Lichtkugel?!), light ball. This wasn't the case however.

It was a lovely word that I repeated several times to the slightly bemused cashier and I was sure it was stapled somewhere securely to the inside of my skull, but as soon as I left the shop, it had escaped from inside my head!

Now I know it wasn't Lichtbirne (light pear) as has already been suggested to me. So any suggestions (within the bounds of decency of course) would be very welcome...