BTX-Squared is probably your best bet for combat use: it can be applied dermally via splash grenade or touch attacks, it can you start getting results after a single round, and those results are pretty spectacular. 2d10+10 damage per round is extremely nasty as you don't have to deal with armour (you can basically consider it as being shot once with a railgun sniper rifle firing AP once a round) and it smacks them with a SOMx2 test to not be paralyzed. Most opponents will have a 50/50 chance at best of making that. The only problem is that it's pretty pricey, but I think it's worth it. My current character has a toxin gland full of it. Mwahahaha.... CR Gas is a low-cost alternative for when you've got other competent combatants in your cell, as it incapacitates pretty well but doesn't do much damage by itself. More for a supporting role. If you can count on solid cover or near-invisibility, Twitch is the ultimate in incapacitating agents. Its primary issue is its 3-round onset time, but a straight SOM test is brutal on anybody, and even people who pass take a -20 to all actions. Those are really the only useful combat toxins, as the others either take too long to start working (Nervex) or aren't helpful in a combat situation (Flight). Against synthetics, you've got a couple of options. Someone here had an idea of putting disassembler nanoswarms in splash rounds and firing off a few dozen at a synth, so the swarms would eat him. Me, I'd say that was of dubious legality, so here's my simpler solution: splash grenades of Liquid Thermite and a pistol loaded with Zap rounds. That'll kill most synths, and a heavy-duty one like a Reaper or Fenrir will be left with no armor so you can shoot it to death easily. Hope that helps.