Yep, The Mighty Worker ... (AND NO, I am *not* a communist ...)
I really like Industrious as one of my two Civ attributes. I will often take a 6-pack (4, at least, 5 is nice, 6 is usually overkill) of workers in an invasion stack, and after landing them with 4 offensive/6 bombardment/4 defensive units directly on or if not possible, adjacient to, a Resource tile. Then hammer out that Fortress. Then pull them out to the ships for diversion elsewhere (not always, depends on the situation of course).
Rapidly building up improvements everywhere, clearing forest for the shields, then replanting forest asap etc. Workers rule! (BTW, once in a great while that cleared forest will be a Grassland with shield, these, I mine of course rather then replanting... now you get two shields like the forest, but with 2 food instead of 1 ... plus the addl. commerce after you get the road built. Somethimes its better for food production needs to irrigate rather then replant forest, but usually I want the shields ...) I wish we had a Combat Engineers unit that could build things like workers, have more defense, maybe couldn't add to pop .... Man, if they could build Airbase (outside of cities) like in CIv II!!!!! This, I really miss!
War units are fun, but the Worker is definitely a key to the game IMHO. Yes, you often wind up with a mighty lot of them in excess, but then unlike war units that give a pittance upon disbanding, you can use the Worker to add Pop to cities ... another reason that they are key. Yea, I will vote for Worker.
Despite what you might think from all that, I usually play pretty miltantly, but I find that without using workers wisely and expeditiously, the odds on conquering the world is definitely lessened .... and usually significantly enough that I fail.