Rule #1 for combat
Making combats specifically against what your players are best at is inherently asshole-ish. If a player revolves their entire character around a specific thing, don't go out of your way to make that thing shittier, just because it is strong. They wont have fun while you do it.
Example:
I played a summon based druid in dnd 3.5. It was low levels so I didn't have a lot of spells or wildshape yet, but my spells were fairly powerful for my level. The DM threw lots of enemies that could grapple me down against me, and I was mostly ineffective against that.
Summoning was also very powerful in low levels, and the DM realized this, so whenever I summoned, I would have to use a move action to command only one animal at a time. The other animals would "act naturally" which means cower in fear of my enemies, doing nothing.
If you screw your players over because you think they are too powerful, they will NOT have a good time. EVER.
Rule #2 extends from this rule.
Have combat where everyone can shine every once in a while. If the players feel useful, they feel good about themselves, so they have fun.
Example:
One player is good at tripping, making him impossible to fight in a 1v1 situation, when the enemy is a medium sized melee character. Put a large "Boss" character that is hard to trip, but surround him with easy to trip mooks. Give your player something to do, even when he is being countered. The party will appreciate the player and understand his contribution to the combat.
Rule #3
Don't have too much bland, "everyone is on equal ground, just beat at each other" type combat.
Have high grounds, low grounds, difficult terrain, cover, etc. Guerrilla warfare is much more fun than marching two armies against each other face to face.
Example:
Flying enemies with aerial cover they cant reach under.