Amazing tactics
Sometimes it happens so that it is worth thinking for 5-7 seconds more before making an obvious and not a bad move, even if it is a 3 min blitz 
One of examples for that might be the following:
White to move ... There is something much better here than Rad1.
Although that was a 3 min blitz, White should have taken not 5, but 10-12 seconds to think over, and to find the way to immediate advantage, quite sufficient for the quick victory. In any case I am glad that after this game I was curious enough to look at this position once more :)
2. One more situation which sometimes may occur and which at a glance may seem nasty for Black. White was happy to grab Black's knight on f6, with threatening mate on g7 ...
... but in reality just one Black's rook move makes things nasty for White, not for Black
3. Here is one more nasty situation for opponent's queen (and for the king, too) ... Even if you have one or two pieces more than your opponent on the board, it does not mean that you are able to prevent disaster when your pieces are lazy, staying at their initial positions and doing nothing
A knight in the center can be stronger than two lazy rooks at some distant corners of the board.
4. Some chess games may last not more than 10 moves, like in the following one: 1.e4 e5 2.f4 ef 3.Nf3 d5 - for now everything looks all right, but after four next moves - 4.ed Qxd5 5.Nc3 Qc5 6.d4 Qb6 7.Nd5 Qc6
there may happen some bad luck for the black queen. Similar nasty positions may occur in different openings, but the mechanism of combined action of the knight and the bishop remains the same, reminding that generally it's not a good idea of putting the queen on the same line as the king.
5. A pinned piece just seems to be pinned ...
... and in reality is not, if there is no king behind that piece. How can White punish Black in this position after Bc8-g4?
6. White to move ... making a draw against the black queen, White even does not need his king for that
A trick like this helps rather often, and not only to make a draw.
7. What is the shortest way to the victory for White here?
8. Here is an example from the Pirc defense.
Like in similar positions of Dragon variation in the Sicilian, White has to be careful with the long diagonal.
9. White to move
The narrow path of several good moves will lead to the position where Black has nothing but resign.
10. Black to move
I played Qh4 here, although with not a bad position, but there is something significantly better here.
11. White to move
It's only the 9th move in the game here, but it's all over for Black already ... When you play the Scandinavian defense with 3.(Nc3) Qd6 as Black, you have to be especially careful about your queen.
12. Here is an example from the King's gambit ... White to move
This is the position from the Kieseritsky gambit (1.e4 e5 2.f4 ef 3.Nf3 g5 4.h4 g4 5.Ne5) - sometimes opponents even in correspondence games play 5. ... g3? here, trying to take the attacked pawn away from g4 (just saying, even 5. ... f3!? is significantly better here).
13. A simple but nice trick here, happened just now in a blitz game, White to move
14. Black to move
White has decided to grab the pawn on f5 just now. Was that a good idea?
15. Black to move
This trick is probably one of the most popular among those who like the French defense
16. When development is neglected, the material balance on the board is not of great importance.
Black to move. How can White be punished in this position?
17. Black to move
Generally it's not good when a piece is "hanging in the air" (a loose piece), not protected by other pieces or pawns. And of course, opponent's "hanging" piece should be a signal to look for ways to punish your opponent for that.
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