Like fisheyes said, the usual build is injector + gauntlet. You CAN take a liquifier, but you'll get more of those per point on wracks, the injecor is also much cheaper and makes a mockery of invul saves. If you really want your talos to be able to deal with hordes, however, take one, they're still a much better choice than chainflail in my opinion, and they're the only unit that can fire the liquifier in melee
There is another option. The gauntlet is recommended because S8 is such a sweet spot (a lot of vehicles/monsters are T7 or 8, and a lot of units are T4), so if you play an experimental creation coven (+1 strenght) or if your talos hang around urien, you can outfit them with double scalpel, you'll still get your S8, lose the -1 to hit, and get another atack, for the price of -1 damage. They'll threaten tanks about as well and be a great Meq killer. The gauntlet is obviously still better vs units with -1 damage however, and AotF is so good that it can be hard to justify.
The only melee option I would never take is the chain flails, 0 ap and 1 damage, even with double attacks, is a waste on a talos in my opinion, we just have so much better options to deal with hordes (anything wych cult, shredders on warriors, trueborn or scourges, cronos, liquifier wracks, liquifier talos, even grots) are all better choices for this kind of job.
As for the ranged options, as said above, twin heat lances are probably the best deal, coven lacks ranged anti tank, not that the other options are bad, except probably the pods. Maybe you can play around a bit more if you're playing dark technomaners, but I didn't find anything amazing with that combo.
They can hang around solo BUT you should take 2 or 3 if you're gonna take a cronos to hang with them, so they can come back to life on a lucky tentacle attack and be healed by your haemunculus next turn