Marines, marauders, medivacs, and widow mines vs Zerg.
Marines, marauders, medivacs, and vikings vs Protoss. Add ghosts when they get storm.
Beyond that we can't really help you unless you tell us what you're dying to. Is it early game? Late game? Timing attacks? Look at a few of your losses in TvZ and TvP and let us know what is killing you and at what phase of the game. Only then can we offer meaningful advice.
Better yet, post replays.