The strangest game I ever had was my Biel-Tan vs Iyanden. Towards the end, all I had left was a trio of Rangers, and my opponent had a Banshee Exarch and two wounded wraithlords...
Needless to say, the rangers won hand to hand vs the exarch and fled into some dense tree cover. With amazing saves on my part and horrible rolls on each wraithlord's brightlance, I eventually killed them both with sniper rifles. Two rangers survived. This was back in the day of 3rd Edition when eldar sniper rifles were normal sniper rifles, so all shots were Saving Throws by the wraithlords.
Another was my tank detachment made for long range vs another detachment meant for cityfighting(and we played nightfight!). Every single tank of mine was useless until I got close and murdererd by all the demolishers and whatnot. At the end, I had an Exterminator and a regular battle tank, which is where I broke out the Gaunt's Ghosts scissor move. Multiple times I pulled it off, getting 3 kills with the exterminator autocannons and 1 with the battletank's lascannon(its battlecannon was gone).
Finally, wayy back at the beginning of 3rd edition, I played guard vs Deathwing. We used special gaming club titan & superheavy rules. I had a baneblade and mixed tanks(with 1 armored fist squad) and he had all terminators and a warhound titan. I got massacred by the terminators' deep strikes into my tanks, which I slowly fought using lascannons and minimum range basilisk shots. The winner was whoever destroyed the other's superheavy. My baneblade was immoble & had no weapons left except a single lascannon turret and his titan had a few wound points left(gaming club rules). With a last ditch effort, I raced my chimera at the warhound, which got it stomped on and destroyed(gaming club rules) and only 1 catachan armored fist survived, with a meltagun. I fired one last death or glory-style shot and hit with a 6, then rolled boxcars for penetration, and the titan took 3 wounds and 'sploded, killing the last jungle fighter, winning me the game with just the useless baneblade left vs about 7 terminators and a terminator chaplain.