Minecraft FallingSand is Strangely Permanent

I figured out how to do this. I use the stat.damageDealt scoreboard objective. First I run the following command once:

/scoreboard objectives add hit stat.damageDealt

Then on the 20Hz clock I do the following:

• First command block:

  /tellraw @a[score_hit_min=1] "Nice Hit!"

• Second command block:

  /scoreboard players reset @a[score_hit_min=1] hit

How this works is that points is added to the stat.damageDealt objective each time they hit/attack/hurt an entity or player. Then it runs the command on every player that has hurt another entity or player. When that command is done, the objective gets reset.

How I found this is that on the statistics menu from the pause menu, there is a statistic called Damage Dealt.

EDIT:

In Minecraft 1.9, use the repeating command block instead of a 20Hz clock.

You can create a lightning stick using these commands in a command block:

/testfor @e[type=Player] {SelectedItemSlot:0}

/execute @e[type=*InsertMobNameHere*] ~ ~ ~ summon LightningBolt ~ ~ ~

You can also create lightning arrows:

/execute @e[type=Arrow,c11] ~ ~ ~ summon LightningBolt

/kill @e[type=Arrow]

To receive a command block, you can type in the command chat:

/give @p minecraft:command_block 64