My best recommendation for under $50 is the Fenix L1D (check out 4sevens). It's a single AA LED light with a few different output modes; they're compact, excellent output, variable output, tail-clicky and pretty tough (I used a few Fenix lights in Iraq with no issues).
Nitcore is another option for $10 more...it's also tough as nails and has a much greater range in output.
Some questions you need to ask yourself:
Do you care what type of battery it uses? AA, AAA, CR123?
Do you want variable output? Something I highly recommend
LED's are just made for rough, outdoors use. They are inherently stronger than any incandescent type bulb without an overbuilt head. They are much more efficient, meaning your battery will last longer. Technology has leveled the playing field with output and light "throw" distance. Most quality LED models have variable outputs, allowing you to select how much light you need for the task. You don't always need 200 lumens to search the bottom of your pack or find your shoes in the tent for a 0300 Mother Nature Call; most of my tasks can be done at 20-30 lumens, but it's still nice to have that 100+ to scare away the boogie man or those damn raccoons messing with our field kitchen! Also, most have an SOS and/or strobe option-mode for signaling which is another good option.
Right now, for your money, I think Fenix gives you the best bang for the buck. They come with a nice little svelte belt pouch that you'll often forget you're even wearing.
Next, you'll need to consider a good LED headlamp
ROCK6