I prefer a steel straightedge and a box-cutter or Stanley-style knife,
with one of those self-healing cutting mats.  The big advantage is you
can place the ruler precisely over the image; you're not trying to see
where the knife-edge is under the print as you have to do with a
guillotine or rotary trimmer.  Also, when cutting heavier material,
guillotines and rotary trimmers have a tendency to skew the item while
cutting, but this doesn't happen with a straightedge.

Colin D.

While there are cheap and good cars, cherap and good cameras, and even
cheap and fairly good printers, I've never yet seen a cheap good
guillotine.

I think the best ones are the big rotaries (usually free-standing!),
followed by the bigger heavy guillotines.  But in either case, the key
factor for me is that it *must* in some way hold the subject down.  The
more expensive ones (of either type) have quite ingeniously simple
safety locks and hold down bars that grip the paper securely and very
close to the edge.  That is the one thing that makes the difference,
imo.

 Dahle

http://www.abc-i.com/cutters_trimmers/rotary_trimmers.htm

Not the cheaper range.

I have an "Ideal" guillotine, of the type used by printers.  Excluding the
handles, it is 590 mm deep, 510 mm wide and 250 mm high, and sits on a bench.
It is very heavy -- I can JUST lift it.  The throat is 370 mm wide by 40 mm
high, and it has a paper clamp, and movable backstop.  My late wife bought it
secondhand through some of her printing contacts for our former business, so I
have no idea what it cost.  However you could ask your friendly printer, or look
for a printers supply company.

It is probably rather large and expensive for the home office, but I find it
invaluable.  It will cut several hundred sheets at a time, so you can buy A4
photo paper and trim it to any suitable size, and you can readily make small
runs of business cards and the like.

Thoroughly recommended!

James McNangle