The dead is probably it. Body type plays a huge role in the other lifts, I've known people who could bench and squat solidly who weren't terribly strong if you grappled with them or had them apply the strength outside of the lifts. It comes down to good leverages more than anything. Now the dead...show me someone with a solid dead and I will show you someone who is legitimately strong. IMO, the correlation between deadlift and functional strength is much higher. The posterior chain is the foundation of strength and you simply won't find someone pulling above 450 who is weak in functional strength.
I guess a case could be made for the olympic lifts and certainly there is a higher correlation to success in sport. Plus, rather than just a basic pull you are pulling, squating, and getting a fair test of upper body stability and power with the jerk or stabalizing the snatch overhead while you come out of the squat. A fair amount of technique and genetics come into play here also but the same holds true. Show me someone cleaning in the 300's and you have a powerful man.
I simply can't say the same for a 300 or even 400lbs bencher nor a 400-550 lbs squatter. Certainly a number will be very strong but I've met plenty that were simply just good at the lifts. The degree to which this happens in the dead or olympic lifts is much lower and I think they represent a better guage of total body strength that is less easy to skew.
Please Scroll Down to See Forums Below 
