Following list (of personally selected symbols) may be used for direct copy/pasting of characters to your code. For many cases, we have much more sophisticated methods (typing math), but still you can enjoy using these symbols in emails for example.
Collection of [http://dejavu-fonts.org DejaVu fonts] contains nearly all characters listed below.
<texcode>
∅ 2205 - empty set
⍉ 2349
Å 00C5 Å 212B
Greek:
áčďéěíňóřšťúůýž
„uozovky“ÁČĎÉĚÍŇÓŘŠŤÚŮÝŽ„uvozovky“ German: ÄÖÜäöüß
Arrows:
⟶⟵⟸⟹➘➙➚➛➜➝➞➡➢➣➤⬅⬆⬇⬈⬉⬊⬋⬌⬍⟵⟶⟷⟸⟹⟺⟻⟼⟽⟾⟿⤆⤇⤒⤓⥂⥃⥄➘➙➚➛➜➝➞➡➢➣➤⬅⬆⬇⬈⬉⬊⬋⬌⬍
←↑→↓↔↕↖↗↘↙↤↥↦↧⇄⇅⇐⇑⇒⇓⇔⇕⇖⇗⇘⇙