Pack Rat, I just love being able to carry twice as many bottles of booze and pieces of scrap metal and cigarette cartons. And it's even more useful in HC mode.
Once I took Pack Rat, I can't believe how I was able to live through playing hardcoe without it. Having it slash all of the little things in weight by half makes it far more useful than Strong Back, in my honest opinion.
Ferocious Loyalty deserves a second mention as some companions have DT's that seem to not be surpassed once you're under half. I even didn't heal for quite some time just because I wanted the perk in effect for my companions. I could take care of myself after all.
For being 'unique' and all:
Nerves of Steel. Apparently, the NV Geck has it listed at 20% increased AP regen instead of the good old 1 HP per 10 Seconds in Fallout 3. I timed it and it seems to actually work around that amount. Sure, in actual fact, its more like shaving off a second or two but you never really know when that second or two is going to come in handy. Add in Rebound, and its VATS spam galore. Definitely didn't regret taking this.