How long have you got?
Loads of models out there but the best come from Leatherman and Victorinox. Gerber and SOG also make some, but I wouldn't bother with them - Gerber's quality is highly variable and the newer models are pretty poor, and the SOGs are a bit of an acquired taste. Leatherman's most recent models have definitely been built down to a price too. A lot will depend on your budget - some of them can be very expensive at list price, but can often be found cheaper online.
There is a file and scissors on the Leatherman Wingman, but they're not very good. It is about the cheapest decent model you can get though, so if you can only stretch to about £40, that'd probably do.
The Leatherman Rebar is probably the best mid-range one - two blades, good file and saw and very good pliers with replaceable wire cutters. No scissors, but you can often get the Rebar in a pack with a Leatherman Micra for £60. Very capable pair of tools, and will do pretty much anything you ask of it. Not quite as comfortable as the Wave to use but a nice clean classic looking tool.
The Leatherman Wave is great (about £75). Easy to open blades, good file and saw, with OK scissors and the bit driver inside - you can get a bit kit for this which will allow you to work on hex/torx/pozi heads too. The mini bit driver is a bit of a waste of space IMO. Comfy to use as well, because of the shape of the handles. You can also get a pocket clip for it which is very handy.
The Leatherman Surge is amazing, but is big (bigger than the Wave, and a lot heavier). Replaceable wire cutters, great scissors, two good knife blades, bit driver, good flat drivers and a blade exchanger which means you can use the standard file and saw but also T-shank jigsaw blades for wood and metal. A proper pocket tool box. Expensive though, about £100.
Leatherman SuperTool 300 -basically a bigger version of the Rebar - it's the same size as the Surge. Very good robust tool, but I found it a bit big and not as versatile as the Surge. Not as expensive though, can be had for £70.
Personally, I'd recommend a Victorinox SwissTool Spirit - the standard model with the serrated blade is excellent. Great quality, good tools (blade, saw, file, scissors, drivers, chisel, awl, etc.) and pairs really well with a Swiss Army knife. Very comfortable to use and very well made. Can be had for about £80. I've got two of these (slightly different models) and they're brilliant.
The Victorinox SwissTool (one of the ones I just sold) is good too, bigger than the Spirit but with similar tools. I sold it because I had the Surge too, and didn't need two big tools.
There is only one to go for, in my experience (sorry it was me that bagged the ones from Chris, for other people), and that is a Leatherman Surge.
Over the years I have owned (IIRC) 3, an original Leatherman, a Wave (way too big) and a Surge.
The Surge is the big one, the Wave is smaller.