Ek Onkar, it is the beginning of the Sikh Scripture, where Ek means One and it is written not in words but in figure like "1" Onkar is combination of three words which means creator, sustainer and destroyer. Together, it tells that there is only one who creates, sustains and destroys.
Please refer to this link for the images of this symbol:
http://images.Google.com/images?q=ek%20onkar&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&sa=N&tab=wi
There isn't really a symbol for Sikhism but now there are two distinctive symbols which are ''Ik Oankaar'' which means ''One God'' in Punjabi and the ''Khanda'' which consists of a double-edged sword(Khanda) , the two curved swords(Kirpan) and the circle(Chakkar). Note the Khanda was never created by any of the Sikh Gurus but this symbol is perfectly acceptable by Sikhs.
The Khanda:
Note: Some people mistake the Chakkar with a Kara(Sikh Bracelet).
The Sikhism holy symbol is called the khanda.
five symbol
Gurdwara
the religion of khanda is Sikhism !
The sacred building of Sikhism is where the Guru Granth Sahib is kept it is also a place of worship it is called the Gurdwara which means the Gateway to the Guru
Guru Granth Sahib.
Sikhism has a sacred test known as the 'Guru Granth Sahib Ji'
it is a symbol that represents Sikhism and is very important to them
A Sikh temple is called a Gurdwara.
The Khanda is the symbol of the Sikhs.
The sacred book of Sikhism is called the Guru Granth Sahib, not Tohra.
Guru Granth Sahib is the sacred scripture of Sikhism. It is considered the eternal Guru and contains teachings and hymns of Sikh Gurus and other saints.
By "Hinduism Symbol" I am assuming that you mean the sacred Aum sound, which is found in many Hindu prayers, religious texts, as well as meditation methods. It is also a sacred mantra in other Dharmic religions such as Buddhism, Jainism, and Sikhism, but originated from the Rig-Veda which forms the backbone of modern Hindu culture and practices.
There is no holy symbol in Sikhism. Khanda is the religious symbol in Sikhism. Please refer to this link: http://en.wikipedia.org/wiki/Khanda_(religious_symbol)