Window of Opportunity is one of my all time favourite episodes of Stargate, and of any TV show, ever made. The episode is great as it puts the focus on the two men of action in the show, Jack and Teal'c, and make them do the stuff Carter and Daniel would normally do.
After being stuck in a time loop, Jack and Teal'c have to keep telling the other main characters each time that they are stuck and to try and work out how to fix it. They then start to translate the Ancient text bit by bit. However, they soon get bored and after perfecting a double juggling act, Jack and Teal'c decide to have a bit of fun instead. Cue the most hilarious scene in Stargate history.
Everything about this scene was great. The now infamous Stargate golf segments were great. "Colonel O'Neill, what are you doing!?" "In the middle of my backswing!" The first official sign that Jack did love Carter was seen in this episode too, with him kissing Sam after resigning in one of the loops. Teal'c getting made at being bumped into each time and pushing the poor guy (I think it was Siler) through the door after snapping is also great. Jack not telling Daniel to watch out as someone is coming every time was also great (something Daniel actually guessed was happening in one time).
This episode was great and funny without the need of parodies (*cough* 200 *cough*) and is in many, many fans best episodes lists, and for a good reason.