My beat-up, flaky-switched, Fenix L2D (P4)*. I really miss the batteries, GITD lanyard end, and trit vial, more than anything.
Prior to that, a Fenix L1P (1st-gen w/ 'partial' regulation), many moons ago.
* In at least one post around here, I'd said L2T. For some reason that was in my head as what it was, but I just came across the 1AA tube, and was an L1D.