The most rugged I have used is a 2006 Peak Caribbean 2AA stainless steel with momentary switch. The combo of potted electronics, brass battery button, lexan window all wrapped in stainless steel made it one tough light. The worse thing I did to it was drop it while up in a ceiling, it fell 17 feet and slammed into a solid marble floor. The battery positive was dented from the impact, the floor was chipped but the light did not even shut off. The downside of the light was it weighed a LOT!
A nice, lighter and brighter replacement that would be as tough (or tougher) would be the Eiger stainless steel with a 2AAA body. It would fit better on your belt but so to will the El Capitan single AA. The twisty on/momentary switch on worked very well and won't/can't break unless explosives are involved.
Once Peak rolls out their multiple output heads with that momentary switch, I'm going to get a few. All I have to do is pick the narrow/medium or wide optics, pick what max power level I want, choose between HA-III aluminium/brass or stainless steel and if I want to run NiMH, E2 lithium or 14500 protected Li-ion for power. I will get all three types of optics, I can choose the beam pattern to fit my changing needs.
I did break an Inova X5 though, it was a great light while it lasted. :(