There's alot of good OD's and distortion pedals out there, and I've had most of them at one time or another. Sounds like your looking for "fuzz" or distortion. The BOSS DS or HMs will give you basic distortion. The BOSS MT-2 Metal Zone will give you that nasty death metal sound - very similar to the DOD FX86B Death Metal pedal.
The Marshall Jackhammer is a very good pedal also - very versatile as far as tone and drive. This is similar to the Korg 105od pedal which has 2 programmable A/B channels for overdrive and distortion - very versatile and under rated pedal. You may also consider a tube pre-amp, such as an old ADA MP-1 or MP-2. The MP-1 costs about the same (used) as a new pedal (around $100.00). Metallica used the MP-1 on the black album. I personally have an MP-1 in my rig (noisy, but great tone, and I'll defend tubes to the death).
...if you hit the lottery, get a MB Triaxis.