Possible codes:

Basic:
[b]bold[/b]
[i]italic[/i]
[u]underline[/u]
[s]strike[/s]
[sub]subscript[/sub]
[sup]superscript[/sup]
[br] Forced line break

[color=blue]blue text[/color]
[size=18]the size of this text is 18pt[/size]
[font=arial]different font type[/font]
[align=right]show on right[/align]
[quote=http://www.server.org/quote.html]hello[/quote]
[code]x + y = 6;[/code]
Links:
http://www.server.org
[url]http://www.server.org[/url]
[url=http://www.server.org]server[/url]

guest@anonymous.org
[email]guest@anonymous.org[/email]
[email=guest@anonymous.org]mail me[/email]

[img]http://www.server.org/image.jpg[/img]
[img w=100 h=200]http://www.server.org/image.jpg[/img]
Lists:
[ulist]
  [*]unordered item 1
  [*]unordered item 2
[/ulist]
[list]
  [*]unordered item 1
  [*]unordered item 2
[/list]
[list=1]
  [*]ordered item 1
  [*]ordered item 2
[/list]
[list=i]
  [*]ordered item 1 type i
  [li=4]ordered item 4 type i[/li]
[/list]
[list=I]
  [*]ordered item 1 type I
[/list]
[list=a s=5]
  [li]ordered item 5 type a[/li]
  [*]ordered item 6 type a
[/list]
[list=A]
  [li]ordered item 1 type A[/li]
  [li=12]ordered item 12 type A[/li]
[/list]
[list=A s=3]
  [li]ordered item 1, nested list:
    [list=I]
      [li]nested item 1[/li]
      [li]nested item 2[/li]
    [/list][/li]
  [li]ordered item 2[/li]
[/list]