Rambo's Rifle
A fantastic primary weapon. It has a scope and it's overall stats are better than that of the SWAT rifle or Marksman (I put less emphasis on mobility than the other stats, and the mobility sacrifice for the Rambo's Rifle in comparison to the other two is minimal). It also has a fast reload time, so I spend less time dodging fire and more time returning it. However, because I have better special/premium weapons, I rarely use it, if ever.
Powerful Gift
I choose this one because it's powerful (two headshots = kill) and has a scope that allows me to use it for long range shots. But, like Rambo's Rifle, I rarely resort to this, since I have better special/premium weapons.
Emperor's Sword
It's the best mellee weapon in every aspect, so this isn't really debatable, unless you hate the look of it for some reason.
Prototype PSR-1 / Chain Thunderbolt
Which one I use depends on the situation. If there's a lot of close quarters fighting, or people are moving about constantly, I use the Chain Thunderbolt, since that thing annihilates players in a half second and has area damage. If I'm sniping, using medium/long range in general or want to hit people moving through lots of cover, I can always trust the one-hit kill shot and obstacle penetration of the PSR-1.
Gravity Gun / Armageddon
I used to use the Armaggedon extensively, but more recently, especially with the new maps, I have favored the Gravity Gun due to the Armaggedon's slow shot speed, which makes it impossible to hit people from afar since they're safely out of the way by the time the rocket gets there, as well as the horrible mobility, long reload time and inefficient and dangerous use for rocket jumping. Anyhow, the Gravity Gun is very useful for 'rocket' jumping, as well as committing suicide at low health so that the enemy doesn't score a point.