How can I type special symbols on my Android device like ☺ or ♥ as a regular character? How can I make special symbols on my Samsung Galaxy SII, like ☺ or ♥?
These are actually Unicode characters you can easily reproduce on your computer:
How can I get “WHITE SMILING FACE (U+263A)” with the keyboard?

The Android platform supports unicode and all its characters, however the soft keyboard that comes with your Android ROM probably won't carry all your desired symbols.

When long clicking on some symbols/characters on your soft keyboard you will see the key pop-up expanding to give you an additional choice of symbols, then drag and release your finger to print them.

Installing some 3rd party keyboards (such as GO-Keyboard) will give you access to more symbols.