Is everything 100% efficient at heating? Everyone always talks about the efficiency of their appliances. I was wondering if everything was 100% efficient at heating its surroundings ?
 A: An electric heater that has "mechanical inefficiencies" as Programmer mentioned will nonetheless ultimately lead to near 100% conversion because things like expansion of wires, creaking sounds etc., will be absorbed by the surroundings and turned into heat, especially in a well-insulated house.
I justify leaving the bathroom CFL light on in the winter (it takes a few minutes to brighten up) because we would just run the heater anyway, and the heat that it emits just offsets electric heating. Similarly for devices wear through on/off cycles.
Appliances can be more than 100% efficient, e.g. heat pumps.
A: Transfer of heat from one source to another can be very efficient. In fact, the first law of thermodynamics says that the internal energy of a system can be transferred as heat of there is no work done through compression, expansion etc. For example, electric heaters can deliver close 99% of the heat energy to their surrounding with minimal loss from mechanical effects such as expansion of the wires. 

Everyone always talks about the efficiency of their appliances.

No. You don't hear everyone talk about the efficiency of heating because efficiency is related to the work output or energy conversion. People talk about efficiency of a water heater for example, to say how much of the chemical energy in the fuel is converted to heat energy. Or an electric heater to refer to how much of the electrical energy is converted to heat.
