I've owned Alot of pistols, and I play with them almost every game I go to.
Pistol play is Fun, but you need alot of patience to get good. that being said, On to the hardware.
Zeus series are Fine, if you don't mind the Brick Size and shape. A properly modded Delta-68 would be your best bet from this series. They're milled a bit lighter, and I like the Snapchanger. Going to replace the Urethane Rings with Teflon.
USP by PMI are my Personal favorite. They take 90% industry standard parts (Spyder internals, PMI blowback frames, Bolts, Etc) They have some drawbacks, like the feedgate (Takes Practice to reload Fast, but it is possible) And the horrid 12 gram change. Again, Slow, but the gun itself is The lightest of all the Semi pistols. And for the cost of a High end pistol, You could carry four of these things, and just play Pirate style.
I own a Tiberius, And they have their own perks. They're not as easy to handle as a USP, but they shoot better, They have a better (And Removable!) barrel, Detents, They're regulated, And they're balanced over the hand. I like Almost everything about my TAG, Except for magazine cost, Mag construction, and Trigger speed. It'll empty your mag before you know it.
All these pistols have huge barrel bored however. You'll need to find big paint, or have the barrels bored for inserts.
Try a few before you buy if you can. And consider the T-9, if you don't want to play pistol, you can convert to a mag fed or Hopper fed rifle.
Really, it all depends on what you're comfortable with. You want to get to the point where you're not aiming a gun, you're pointing with your finger, and people put their arms up, With paint on their masks.