Any where the stunt doubles aren't obvious on even a 15" color TV with a horrendous 0.3mm dot pitch that was standard in 1967. As much as I adore "I, Mudd", that fight scene is one of the worst and they didn't bother to use angles to hide the fact Norman went from a somewhat meaty and delicious mid-30s android body to a thinner, faster, yet early-50s stunt double android body - complete with a completely different (and shorter!) hairstyled model in a number of cuts to ensure the added mass and related weight wouldn't cause excess drag factor to slow him up... Silly laws of physics...
But one of the best from TOS? Kirk/Mitchell didn't look too out of sorts with the stunt doubles.
Totally agree, my favorites are those where the stunt doubles are either well hidden or not there at all. When Shatner did his own fights, they were amazing. He had great physical prowess and a great flair. He could really throw a powerful stage punch. With that in mind:
1.
Tomorrow is Yesterday: all Shatner and a lot of fun. A gripping fight while still being lighthearted.
2.
The Gamesters of Triskelion: Shatner did all of his own stunts here and the fights are really nicely done (even when he misses the colors he's supposed to hit). The teaser, when he fights Lars, is great. Watch how he dodges the knife and then hammers Lars with a left and a right. It's a shame Shanna couldn't have defeated Kirk more convincingly.
3.
The Omega Glory: OMG this is the best of the Shatner brawls. He and Morgan Woodward are fantastic. Woodward powers through his blows and Shatner handles all of it with great athleticism.
4.
Spectre of the Gun: fun! Shatner does his flying kick and then actually winds up his punches, raining blows upon Wyatt Earp.
5:
Whom Gods Destroy: Kirk vis Garth as Kirk. The BEST double I've seen for Shatner. They FINALLY fitted the stunt guy with a Kirk toupee and found a guy with the same build. Some shots are very difficult to see who is whom.
Journey to Babel almost makes this list, but the flying butt slam and Kirk keeping his back to the guy with the knife was just unforgivable. There was a cut scene posted here some time ago that joins the fight a few moments earlier. It was actually pretty exciting because it started with a tracking shot. The whole thing was mostly one take, which is great too. So you know, maybe it deserves to be on the list. It's still better than the "tall skinny guy as Kirk" fights we kept seeing.