Ah... mine is with the ball of the foot as the primary tool, so we're probably talking about 2 different front kicks.
Anyway, as far as the strike that can be counted on in all situations... I can't give one; there are too many situations in which a particular strike would be less effective or not effective - or appropriate - at all.
I'm with Kacey, here... There are too many strikes that can be effective for certain situations. However, if I had to pick one that I feel that I personally need to work on, is the jab. It just doesn't feel right, so that's what I'm really working on at the present. Basically, I think you should work on every aspect of your art- kicks, punches, etc. to perfect them or refine them a bit more. Even if they look great.