Syndicate is a cracking mix of strategy, action and RPG that gleefully throws morals out the window. It works on plenty of levels - the missions themselves being immense fun, co-ordinating your team of agents as they infiltrate the various levels and letting loose with a wide range of destructive weaponry. The sound and animation that goes with the shotgun is incredibly satisfying, to name just one thing. But then there's sniper lasers, rocket launchers, flamethrowers (who could ever forget the agonized screams of a flaming victim?). You can even steal vehicles and use them offensively.
The other side of the game is the company and team management. Thankfully the company economics is kept down to managing tax rates and making sure the countries you've captured don't revolt (this simply means having to re-do whatever mission is necessary to recapture it). Team building (literally) is a ton of fun. Your company uses its funds to research new technologies. Weapons, bionic upgrades, high-tech equipment. Everything your team needs to grow and take on the increasingly challenging missions. It's very satisfying to mould an agent into a super-fast, near-indestructible killing machine from the weak and vulnerable assassin that takes on the first mission.
With a great deal of replay value in the missions, Syndicate is a true classic that's still fantastically good fun today.