First of all, if you're serious about wanting something more or less the shape and proportion of a cigarette, stay FAR away from the pro-vari. Two of my coworkers that I turned on to vaping recently got the pro-vari, and while they are both EXTREMELY happy with it's performance and build quality, there is no way around the fact that it is HUGE! Quite frankly, it looks like a screwdriver. A screwdriver with a very heavy handle.
It does not resemble a cigarette or cigar in any way. It has almost no resemblance to any smoking device I've ever seen, except that it's about the size of a small .....
If you want the same diameter as a 510, but you're okay with a little extra length, you might check out the Infinity Ion from revolvercig.com
On the up side, 4 of the 5 people I know who bought one have kept up with it and all love it. The 5th liked it very well, but wasn't able to transition from analogs. Everyone I've talked to who has used both a 510 and an infinity Ion has agreed that the Ion is significantly better. I've bought quite a bit of stuff from them, and they're good people to deal with.
On the down side, it uses a non-standard threading, so as far as I know, you can't buy anything for it from a 3rd party. That means you're locked in to buying everything but liquid from revolver.
The other thing you should consider, and several people have recommended, is something cigar-sized. I've personally used the Vgo, eGo, Leo and Lea.
My current favorite is the Lea, and it does use 510 threads. However, it comes with a proprietary tank atty and some people have found that not all 510 threaded attys will work because of the air path. It's the narrowest of the bunch, but still much thicker than a 510. With the cap on it, it looks like a fountain pen.
The Leo is generally a love it or hate it e-cig. I loved mine, but I love my Lea more. There used to be only one atty option for the Leo, but there are now regular and LR attys, cartomizers (up to 4ml) and tank attys. This is the largest of the ones in my list, and is comparable to a medium/large cigar. It also has a cap like a fountain pend, but it's too big to fool anyone, and there's no pen clip.
The eGo is the logical next step for many vapers looking to move up from a 510. The standard eGo uses 510 threads, and any 510 atty or carto will work on it just great. It's thicker than the Lea, but thinner than the Leo. Because of it's atty threads and the threads where the cone attaches, there are MANY options for this one. Without even thinking I could probably list off a dozen types of attys and cartos for it, and that's not counting the fact that most of them are available in different resistances and/or from different manufacturers. Without a doubt, the eGo is the most flexible of bunch. However, it's very simple in terms of looks, too thick to be a cigarette, and too short to look like most cigars (unless you get one of the larger battery capacity versions, which are a bit longer) There are also some very good eGo knock-offs like the Riva 510, which are fully compatible. Just make sure you get one that has a threaded atomizer cone.
The Vgo is one of the more common names for a cheaper eGo knock-off. The number one thing to look for here is a non-threaded or "push on" atomizer cone. This will greatly restrict what accessories you can use it with. If you're really certain that you'll want to stick with 'regular' 510 attys and/or cartomizers, the Vgo is fine.
