They don't make rap songs like they used to.
Remember that first joint w/Ja, DMX, and Jay-Z? "It's Murda". That's a hardcore song.
DMX will probably be the best source here. "Bring Ya Whole Crew" "No Love 4 Me"...there's a lot.
Pac got some that will amp you up - "Troublesome '96" "They Don't Give A Fuck About Us" "Hell 4 A Hustler"...
But in all honesty, nothing comes close to 50 Cent's shit off "Get Rich or Die Tryin" (try "Heat" "What Up Gangsta" "Many Men") and that first GUnit album "Beg For Mercy". Plus Buck's first album - with "Stomp".
TechN9ne has some adrenaline-pumping stuff, but there's a reason the artists I mentioned above have made it big - because their shit is killer.