I have an electric guillotine, some chines thing, costed me 1000 euros, and it's cut area is 450 x 470 mm - I got it 'cause I have a small run laser print house, and provide complete laser printing service.
Now, I do cut vinyl decals on it, but there are some problems:
1: minimum cut length for my guillotine is 5cm (2''), because it has press on it - a peace of hard iron to pres paper so it will not move or anything like it. Most of electric guillotines have a press on them, therefore, they have minimum cut area
2: glue from vinyl is coming from sides of decals and remain glued on guillotine knife, which deteriorates cut quality, and it must be cleaned often.
There are also smaller manual guilotines, some - better ones, have a press, therefore - same problems as above, other do not have a press, but U can only cut few papers/vinyl decals.
Second one mentioned U can buy for, like, 50$ or so, but, I'm not sure how much different it is from doing it with scalpel.
As for guillotines - IDEAL brand is a good choice if U want quality, durability etc.
Though, I am pretty happy with my chinese no-name one (acctually, it has a name, but of a company I bought it from, so, good chance is U can find one who import them under their own name - there)