No no no! Giga Impact should never be used as the primary STAB attack! sure, you may think that because of Truant, if has to skip a turn anyway, but Giga Impact FORCES you to stay in battle, whereas using Return or another move allows you to switch after you attack.
So basically, only consider Giga Impact a SERIOUSLY last resort move if you expect not to last to the end of the turn. Return, Body Slam and even Retaliate (since Slaking is often used as a really hard hitting revenge killer with a scarf) are better STAB choices.
Also, I hope there's going to be a little section on Vigoroth as well?
Beautifly are my Bishie!
hands off or my Beautifly's shall take you away and have their way with you!