I have a fairly sturdy high-density plastic one, when I get back from work tomorrow I shall check which manufacturer.... If you can find a steel one, however, go for that, as having a rigid base (the bit with the blade that you slice things on) is very helpful.
Also helpful is the advice about using the guard. I now have a 2cm scar on my right thumb from enthusiastically slicing up an apple to make apple-crisps with, only forgetting to stop in time before adding a few 'unorthodox' slivers into the mix..... Damn sore for weeks and put an end to guitar strumming for a coupla months!!!!
Oh well, at least I havent done that again!

Cheers,
Adam