Best items? Hoo, boy. So, this depends on one of two things:
1) Viability
Things like the
Mummy Suit come into play here, because it's a powerhouse of a suit simply due to the fact that it has 3 lives, with very few ways to actually circumvent this without the player who's using the suit being more or less stupid in their approach - for example, the tripmine approach allows someone to rip a mummy because the person has to respawn on said tripmine, which they'll die to every time.
Another example is the
Gluon Gun, which is a player favourite, and has remained as such over the years. The weapon boasts an enormous power and shreds through suits and players like it's nothing.
If you're looking to raid, what do you use? Well, you have several options, but most people will generally go for the
Portable EMP, even to this day. The
Nano Suit has the ability to hack keypads, but at least you don't have the added risk of losing a suit if someone sneaks up on you.
A final mention might be basing items, like printers - the glory days of using a quad-boosted Ice or GPP, because those were the best two printers of the age before things like the Skull, XMAS, Hell, and Summer.
Or the Medishield/Baseshield/Radshield. A terrific trio that offers a triumvirate of protection from everything from handcannons all the way to a damned nuke!
Special mention goes to a Tactical Insertion Point, which - while a one-use item - is now widespread enough to *still* be an old fan favourite. Feel unsafe in your base? Put one down, and you'll respawn where you placed it, ready to keep kicking ass.
2) Personal enjoyment
There are some items that just tickle an itch, even if they're not the most economically viable, or even the most smart to use in the moment. There are three that I hold near and dear:
A)
QED
The Quantum Entanglement Device is a massively telegraphed grenade that is worth more than CS grenades, and is an insta-kill to the majority of suits. It creates a black hole, pulling everything in and vaporising it.
Thermal Detonator
Remember being in the Nexus, throwing like 20 of these on someone and having them raid someone's base? The resulting explosion killing the majority of the basers before they know what happens, and then the rest of the raiding crew coming up to finish the job? That's the brutality of this amazing weapon before it got nerfed by being unholsterable.
C)
Valkyrie
It was between this and a Laser Dagger, but I get far more enjoyment out of
RDM'ing people legally killing an enemy with a
surprise rocket to the face from halfway across the map than I do blowing people up with a surprise knife explosion...