I somewhere read that an action sequence needs more than just a static battleground. This is as true for an RPG as it is for any movie - you better have something going on around you, surroundings influencing things, hazards, all that jazz. So this week, I had my players fight - in a pit.
Good action movies know that the set is as important as the action that takes place in it. Take anything Jackie Chan does, for example. The sets and props really take center stage. If he could get a hovercraft for a day, you better believe that there will be a way to integrate it into the plot. The best action scenes are running gun-battles or fighting on a moving train or scenery falling down around the characters, threatening to crush either combatant at any moment. This is something where computer RPGs often fail - and so does traditional gridmap DnD.
You CAN put rules into the game that make things more interesting. Say, this and that hex/square/area spout hot steam every X turns, doing damage. Often this just creates no-go zones for PCs and enemies. If you present an enemy stupid enough to run into danger face-first, the battle threatens to become a riddle. Where do you need to place yourself in order to lure the monster into X? That's why I prefer freeform storytelling in battles, sprinkled with some dice-rolls to keep things unpredictable to both the players and myself as the game master.
The two surviving PCs of a small foray into ancient underground ruins were fleeing. Their friend lay dead, killed by their own bullets, in a crypt behind them. The monsters were chasing. The underground complex terminated in a huge drill-shaft. To get back topside, they would have to climb - there were rusted metal bars forming a ladder, alongside which a steel cable was hanging. The group had used the cable to secure themselves when they were climbing down. So one of them took to the ladder, the other tried climbing the cable, when the praying mantis-like aliens emerged from the tunnel right beneath their feet.
The battle was a vertical chase between the PCs, armed with firearms with little or no ammo, and the aliens that were limited to their raptorial legs. It was tossing down empty guns onto the following monsters, rolling for stamina to stay ahead, rolling acrobatics to swing over to the ladder etc. In a desperate last-ditch, one of the two, the teams socialistic terrorist bomb builder, hung herself upside down by her injured legs to fight one of the monster hand-to-hand - and won. The interesting part was the verticality: You could lose your grip and fall, and there was no regular trading of blows with something that is hacking at your legs.
Thanks to some astronomic luck in dice-rolls, both PCs got out of the hole alive, although said revolutionary almost bled to death on the way up. I really liked the vertical battle and will implement such features more often n the future. Tactical inequality is always nice. The only thing the whole thing was missing was moving parts, like enormous drill looming above coming to life or something but the industrial plant on that planet had been left alone for eight decades. I couldn't imagine it still working, as scavengers had picked over it and ripped out all useful parts. Well - next time.