Slash Charger is a very insidious card since the opponent might not even realize how big of an effect it had to the game. One can use it to eliminate Bazagazeal, Clamp etc. before your opponent is even able to use them. It really gives Transmogrify, Rebirth and Live and Breathe hard times of doing what they are meant to be doing.
Of course, against rush decks Slash Charger is pretty useless (although you still get 1 mana), but not very many great cards are.
Slash Charger can have huge impact on the game for just 3 mana (and being a charger too).
Its a great card no doubt