I've played every R&C game from the first to Dealocked. I still own Going Commando, Up Your Arsenal, and Deadlocked. It's the first PS2 game I've ever played and it's to date my favorite series of all time. I've gotten all the unlockable content from both Going Commando and Up Your Arsenal, including all the gold, platinum and titanium bolts. It's a fun game, but Up Your Arsenal was way too easy. And Deadlocked was too short. There were only 14 planets in deadlocked as opposed to over 20 in Up Your Arsenal. My favorite game in the series though was Going Commando. The worlds were more creative and fun to explore, and the weapon selection from R&C2 was GIGANTIC! And for anyone who's familiar with the series, I'd like to know your top favorite weapons. Mine in no particular order are:
The Meteor Gun from Going Commando (With the Lock on Mod)
The Mini Nuke from Going Commando
The fully upgraded rocket launcher from Going Commando (Can't remember it's real name)
The second RYNO (I hated the third one from Up Your Arsenal)
The Harbringer (Of course)
And for anyone looking to learn more about the series, I suggest going to it's Wkipedia article.

For some reason there's no longer an article listing all the weapons.
Ratchet and Clank Wiki