Certain foods are often restricted between borders as a way of controlling the spread of disease and pests.

Plant and plant materials are often restricted.

Weaponry of various and sundry sorts are not allowed in many countries.

It is a good idea to look up the immigration websites of the countries you are thinking of visiting to see what they do and don't allow.

Here are some useful resources:
http://www.voyage.gc.ca/preparation_...n/menu-eng.asp
http://www.voyage.gc.ca/publications/bon-voyage-eng.asp
http://www.voyage.gc.ca/countries_pays/menu-eng.asp
http://www.intercultures.ca/cil-cai/...uspays-eng.asp
http://www.customs.gov.au/site/page4224.asp
http://www.customs.gov.au/webdata/re...Travellers.pdf

Here is Australia's immigration website, for example. From here you find information for a visitor's visa, which you would need to enter Australia.
http://www.immi.gov.au/

And here is where you'd find what you cannot bring into Australia.
http://www.daff.gov.au/aqis/travel/e...alia/cant-take

Here are the Australian government customs pages with regard to weapons and other imports.
Weapons - http://www.customs.gov.au/site/page4372.asp
Other imports - http://www.customs.gov.au/site/page4369.asp


If you do your research before you go, you'll know the answer to your question. Oh, and when you look up sites, make sure they are government sites and not just some tourist site. The government site will have the most up-to-date, accurate information.