I don't sprint a lot, although on rare occasions I would pull out on hill climbs.

I try to set my tension to close to the maximum tension that allows easy clipping in, which usually is enough to keep from unclipping. (make sure you have good pedals and cleats). Getting out is easy enough.

There are a few brands of pedals that are very light.

Xpedo R-Force, and the Xpedo M-Force 8 pedals with titanium spindles are quite light.

I think I've worn down the R-Force pedals slightly and have pulled out from the left pedal (my general unclip pedal) a bit. So far no problems with the M-Force 8 pedals, although they are very grippy, and will grab onto the shoe anywhere.