Commandos is such a great series. More RTT than RTS, it's all about taking a small squad behind enemy lines and making the more of your team of elite soldiers. It's also bastard hard.
For the next 23 hours, you can snap up all three Commandos games, plus the two Western-themed Desperados that incorporated the same style of play, for just £3.75 over at GOG. Alternatively, you can buy them individually starting at 70p.
If you're a fan of tactical games, I strongly urge you to check these games out if you haven't already. They're brilliant.