Most of the sampled songs I like are because of the instrumental more than the song as a whole, but here's my list:
1. Big L / Tupac - Deadly combination
2. Nipsey Hussle "Hussle In The House"
Awesome sample from Kriss Kross' "Jump"
3. The Game - "Down"
Always liked this sample. Game goes pretty hard on it too
4. Pete Rock & CL Smooth - "Straighten It Out"
5. Busta Rhymes - "In The Ghetto"
In the Ghetto - Busta Rhymes / Rick James. The simplicity of this beat is ingenious, one of my favorite instrumentals. Rick James vocal samples are just a bonus.