One man's "doesn't feel like a tank" = another's "gads, you expect me to run in that?!" At what point on the spectrum are you comfy? Some models I've worn in recent years, from more shoe (top) to less:
Brooks ST - really more of a light LWT, not bad but I really grew to prefer true flats. I wasn't crazy about the medial post (still there in current version?) or the relative inflexibility.
Nike Free 5.0 - heel's a bit trainer-like in height, I'd check out the 3.0 instead these days. But it's comfy, light, and it's been durable for me. And flexible enough? Duh!
Fila Corsa Sette/Otto - nearly as flexible as the Free, a tad lighter I think, lower heel, super cushy for a light flat. Lots of arch support for a flat. Some find it too spongy. My favorite shoe, period. For me, it's cushy enough for daily training and road marathons, light and low and flexible enough for trails and tricky footing. Depending on your size you may still find the Sette on closeout; I just picked up another 3 pair.
Nike Streak XC - nobody's calling this a tank or a brick, except maybe someone who only runs barefoot. I might wear it full-time if I ran fewer pavement miles; the cushion is fairly minimal. Similar to the Ekiden but more flexible and a bit skimpier.
Nike Waffle Racer (original 2004 reissue) - less cushioning than the streak XC? Probably, though I haven't worn 'em in quite a while. Obviously great on grass and dirt trails. Seemed durable except I think too many road miles wore down the waffles a bit.