It depends on the game I am playing. In 3rd gen, (RSE for those who don't know) it is (big duuuuuuh here folks) trapinch/vibrava/flygon. also I like ralts/kirlia/gardivoure, mudkip/marshtomp/swampert, and aron/lairon/agron
In Diamond, I like the extremely versitile shinx/luxio/luxray and a whole group of others. IMHO the fourth gen are the best. (Strength, Durability, Versitility in most of the new 4th genners.