Setting the law and public perception and all that hulabaloo aside (get off the Daily Mail/anti daily mail band wagon and stop rehashing the anti knife rants that litter the forum already!). Lets just think about the naked question that galavanter, a pretty new member, has asked.
'An alternative to a knife'
Taken IN THE SPIRIT OF BUSHCRAFT that could well mean that you have lost, forgotten or are trying to do without your knife for what ever reason (heck, I have often found that I need a knife but have ventured out with the wrong trousers on and thus no knife!). In that case, an alternative must be sought
If you have the facilit and ability to knap flint, then you can fashion a cutting tool from any ceramic, glass or suitable stone you may come across. Other alternatives would include an axe, a shovel, even broken bone or a spoon. The 'knife alternative' could be all sorts depending on what you need to cut. I've used a stone to abrade though a rope because I had no blade, I've also used string to cut another string when feeding haylage to to horses ('sawing' through the bailing twinie with another piece). Fire can be used to cut a long log into shorter logs, or to cut a piece of antler in two.
There are lots of knife alternatives if you put your mind to it. With regard to taking an alternative to a knife with you in the first place, I think unless it is an edged tool in the first place (or the kit to make such a thing) then you are most likely just making life very difficult for yourself.