pretty much any of the classic pump shotgun designs like the Remington 870, Winchester 1200/1300, Mossberg 500, Ithaca 37, etc can be counted on to be reliable and durable.
if you are looking for a tactical style shotgun you would be better served with an 870, however, since there are
far more aftermarket accessories available for it than anything else.
check out Can-Am's Dominion Arms Grizzly line. they are 870 clones that fit almost all 870 parts, and are a steal at ~$300 incl. shipping. i picked up a 12.5" barreled one from him at Christmas, it came with a pistol grip in addition to a regular stock, and id go so far as to say that it is actually more sturdily built than the current Remington 870 Express line.
and no, i dont work for Can-Am
im just happy with my Grizzly.