Actually, going at least vaguely serious, there is one that tends to pop up in many fan 'versus' spheres. That of one side being fully-equipped, well-rested, at the peak of training, having a good day, and generally otherwise being at their best, while the other side is either mediocre or strangely inhibited.
Just to keep it going both ways, a Warsie doing this might claim in, say, the <i>Enterprise</i> vs the Death Star...
'OK. Well, the Death Star has loads and loads of troops on board, and hundreds and hundreds of TIE fighters and other ships - and since some sources say they can carry either six or two projectiles, that must mean it's eight, and every Empire soldier on board is powered by the Force. And the <i>Enterprise</i>, well, since we know they have a repair cycle, it's unlikely they'll be at the top of it, so they won't be in good shape. So they probably don't have many torpedoes either, and they don't like fighting, so half of them will have abandoned ship...'
A Trekkie doing a similar thing might claim, 'The <i>Enterprise</i> will have a team standing by all the replicators manufacturing torpedoes, and forty-seven other ships, all of which are <i>Defiant</i>-class, will be sitting right inside the next star because they all have metaphasic shields... TIE fighters or X-Wings won't be around because they wouldn't come to the battle. Now, we know it takes about six and a half weeks for the guns on the Death Star to warm up...'
For some reason this is a favourite to pop out in any kind of [Whoever] vs Batman argu--ahem, debates. Batman's inevitably spent the last three weeks scoping out the territory and planting things, whereas the opponent doesn't know that she's supposed to fight today, and is probably drunk or mind-controlled so not at her best. Or something.
There's someone in every camp that does it, really...moving on...