Soundwave

Like Starscream, most people underestimate Soundwave. Yes, I admit that having an alt-mode that's a tape deck is....not all that fantastic. But think about it, he IS Megatron's spymaster and on earth, a tape deck wouldn't be out of place. But let's get on with his story, shall we?
In the G1 series, Soundwave's beginning is not given, but in The Transformers: Megatron Origin (which is a great graphic novel, by the way) Soundwave is introduced as a 'bot who wants to join the Decepticon cause only so that the weapons he invents will be used for destruction. Very few bots trust him and with good reason: Soundwave's closest allies are minicons used for spying and infiltration. If Soundwave views another Decepticon as a threat, he will send out his minicons to find whatever information he needs to have them destroyed, and they are always successful.
That being said, Soundwave has ten minicons but mostly uses only four of them. Their alt-forms are, of course, cassettes.
The four that he uses most often are Frenzy, Laserbeak, Ravage and Rumble. These four are a constant problem for the Autobots in battle. Frenzy, while small, is absolutely fearless, which throws his opponents off-balance. Laserbeak is agile when in his bird mode, and his small size makes him hard to detect and the perfect spy. Ravage is incredibly smart and stealthy. His robot mode is that of a jaguar and he uses it to his full advantage. Last is Rumble, who, to be totally honest, nobody but Soundwave and his other minicons like even a little. He's obnoxious and full of himself, but he is also an invaluable member of the Decepticons. Why? His arms transform into what are essentially pile drivers that can cause localized earthquakes that have ranked as high as 5.4 on the Richter scale.
Other than those four, Soundwave also has Squawktalk, Slugfest, Ratbat, Beastbox, Buzzsaw and Overkill, though they aren't seen in the G1 series.
The Soundwave most of you know and love is seen in the modern Transformers films. In the first movie, he was seen taking over a military satellite and handling all inter-Decepticon communications. In the second movie, he ejected Ravage to steal the shard of the AllSpark that was being kept “safely” at a military base on Diego Garcia. Stupid humans…thinking they can keep anything safe from the Decepticons……
Anyhow, aside from the minicons, Soundwave is much stronger than the average Transformer, not to mention much more intelligent. His ability to detect any kind of communication has made him the perfect spymaster.
Soundwave's only weakness lies in the fact that very few Transformers trust him, which suits him just fine. He doesn’t need them to like him, just obey him.
Bumblebee ;)