In one campaign, counterspelling was one of the most common actions used by the spellcasters. The premise of the campaign was that the evil empire that controlled the world had a magical secret police force of orcish mages and clerics called the Inquisitors, who were all specifically trained to counterspell.
They couldn't cast high-level spells, and their save DCs were crap, but they could hit 3rd level spells for Dispel Magic, and they all had Improved Counterspell and (from Forgotten Realms) Reactive Counterspell, which lets you counterspell as an immediate action, but you give up your action in the next round. They wore bearskull masks, and were accompanied by at least four warriors at any time, and they would track down and kill any mages disloyal to the empire.
It helped that at the beginning of the game I had told the PCs that they all had to be spellcasters or have some close tie to a spellcaster. They hated the inquisitors. Their first encounter against them was in a flaming forest that the party had tried to cut through to evade their pursuit. The PCs and the orcs were all warded with resist energy, and when the orcs caught up, the inquisitor started by dispelling their fire protection. Then he just stood out in the open, with one bodyguard protecting him, and he waited to see if any mages cast spells. He countered three spells that fight, things that would have turned the tide in the PCs' favor.
What I loved, though, was that one player was especially cunning, and he actually developed a suite of tactics for defeating inquisitor tactics. He would always cast spells while behind cover if he could, to make it harder for the inquisitor to identify the spell. He wore a long coat with a fake right arm tucked into a pocket, while his actual arm was concealed under the coat, so he could hide his somatic components and feint to pretend he was casting. He developed a feat (the game started at 5th level, and he made this as soon as he reached 6th) that let him 'pump fake' a spell, wherein he'd do the first few words and gestures of a spell, pretending to cast it with a Bluff check, so if the inquisitor failed a Sense Motive check, they'd try to counterspell the fake spell. Then the PC would cast his actual spell.
The main villain of the campaign was the 20th level wizard who had started the inquisitors. She would cast quickened spells and still be able to counterspell. She could deflect the PCs' spells and take control of them. She basically made magic her b*tch.
The PCs had an interesting method for killing her.