Horse Archer armies are especially fun at the beginning, though they're a bit too strong vs. the AI and give a great strategic advantage as they suffer few losses. Later when I can build good balanced armies I like to use them as well, usually mixing up elites and weaker units to make playing more fun. Archers/crossbows/gunpowder units get quite a few of the kills. I let infantry slug it out and use cavalry mainly for cavalry vs. cavalry and hunting missiles.

I don't use artillery too much, cannons I use when they appear, but in field battles mainly Serpentines, and I usually autoresolve settlement assaults anyway.