According to the MUL, the list of 100t mechs with TSM and no Melee weapons is: Atlas AS-8D, Pillager PLG-5Z, and Vanquisher VQR-7U. For me, it would be a toss-up between the Atlas and the Pillager. The Atlas has better medium range damage, but the Pillager has stealth armor. However, while the 100t+TSM mechs will give you the largest amount of damage from a punch or kick, they are a bit slow.
For a Melee mech, I would like to see a base, non-TSM speed of 5/8 or 3/5/5 if improved jump jets are an option. Still want TSM though. It literally doubles the damage, and there is no getting around how powerful that is. Looking at those criteria, the first contender is, oddly, the Hammerhands. Both the HMH-6D and -6E are 3/5/5 and have TSM. They aren't perfect though, as their major weapons are also in the arms, so really these are best for kicking and not punching...at least until you run out of autocannon ammo. The next steps down, the Thunder THR-2L and Excalibur EXC-CS have the same problems though, and are 5t lighter, so really the Hammerhands is a solid choice. Further down the weight scale, you get the Thunderbolt TDR-60-RLA which is 5/8/5, has TSM, and all its weapons in the torso. Not bad at all for fisticuffs.
I don't like going much below 65T mechs because, even with TSM, you start getting damage that is awful close to what a non-TSM'd assault could manage. You do pick up some speed, but I just feel that you end up being in too much danger from a return melee attack once you get down to 50t-55t. So, the TSM OstSol's are about as low as I would go. Plus, when you go smaller, there are actually very few mechs that have TSM but don't have a melee weapon of some sort to go with it. The ones that do exist tend to be pretty rare for one reason or another. If you start looking at 50t and smaller mechs without TSM or melee weapons (or both!), your physical attacks get unimpressive real fast.
All that said, the TSM Berzerker is still probably the most frightening melee mech out there if you ask me.
