Sending and receiving different types of data via I2C in Arduino
I2C is truly a powerful option of Arduino, for too many reasons; yet the amount of tutorials available are not that many and unfortunately are too complicated for the average person. 

After working on this for 2 days, I think I have a way to transfer pretty much anything between master and slaves and viceversa. Note that I2C does not transfer floats or even integers larger than 255, there are several ways to go about this and here is a good tutorial 
http://www.gammon.com.au/i2c
and even a library: http://forum.arduino.cc/index.php?topic=171682.0

The solution I found was simpler. Basically we convert any value, string, number, text, float, you name it, and turn into a variable char, which can be transferred via I2C. Once transferred, you can convert back to a number although in my case below, I just wanted to display the data from the slave. 

Here is the code. I provide comments on different parts for clarity. I hope this helps. it worked for me.

//master
#include &lt;Wire.h&gt;

char t[10]={};//empty array where to put the numbers comming from the slave
volatile int Val; // varaible used by the master to sent data to the slave

void setup() {
  Wire.begin();        // join i2c bus (address optional for master)
  Serial.begin(9600);  // start serial for output
}

void loop() {
  Wire.requestFrom(8, 3);    // request 3 bytes from slave device #8

//gathers data comming from slave
int i=0; //counter for each bite as it arrives
  while (Wire.available()) { 
    t[i] = Wire.read(); // every character that arrives it put in order in the empty array "t"
    i=i+1;
  }

Serial.println(t);   //shows the data in the array t
delay(500); //give some time to relax

// send data to slave. here I am just sending the number 2
  Val=2;
  Wire.beginTransmission (8);
  Wire.write (Val);
  Wire.endTransmission ();
}


here the other part
    //slave

#include &lt;Wire.h&gt;

char t[10]; //empty array where to put the numbers going to the master
volatile int Val; // variable used by the master to sent data to the slave

void setup() {
  Wire.begin(8);                // Slave id #8
  Wire.onRequest(requestEvent); // fucntion to run when asking for data
  Wire.onReceive(receiveEvent); // what to do when receiving data
  Serial.begin(9600);  // serial for displaying data on your screen
}

void loop() {
  int aRead = analogRead(A0); //plug a potentiometer or a resistor to pin A0, so you can see data being transfer
  float x = aRead/1024.0*5.0; //generate a float number, with this method you can use any time of data pretty much 

  dtostrf(x, 3, 2, t); //convers the float or integer to a string. (floatVar, minStringWidthIncDecimalPoint, numVarsAfterDecimal, empty array);
  Serial.println(Val);         // print the character
 delay(500);
}

// function: what to do when asked for data
void requestEvent() {
Wire.write(t); 
}

// what to do when receiving data from master
void receiveEvent(int howMany)
{Val = Wire.read();}