I use a cricut trimmer. I liked it at first but the blades have become difficult to find. Only M's ever hasthem in stock. Also the guide has become warped and I have to be careful or it cuts crooked. A new one is on my list. My other Fiskar tools have been awesome so I'll probably go that route.
I like my fiskars triple track trimmer. I prefer it over a guilotine b/c I can cut holes in the middle of my paper which you can't do with a guilotine.
Also, this version fixed the problem of the blade slightly warping that old fiskars trimmers had. I've probably had this one for 4-5years and it still works great. Some of the grid lines where you lean rubbed off but I just used a slick writer to draw them back on. Good as new.
It's light, portable, has a fold out ruler, gridlines and replacement blades are easy to find (M's).
I have three trimmers. No, wait. I have five!!! Holy cow. I only use three of them consistently, though.
I use my Making Memories trimmer at home. I love it. Smooth cuts every time. It is big, bulky, and rather heavy, though. However, I like that I never have to change the blade and since I don't do much more than lift it to put it on the table to cut, then move it out of the way, the weight doesn't bother me. I use it for cutting larger than 6" pieces of paper. For trimming pictures and smaller papers, I use my Creative Memories personal trimmer that has been going strong for at least 5 years, probably longer.
For crops, I use the Fiskars trimmer. I have the orange one. I don't really care for it because it's harder to tell where the blade will cut than it is on my MM trimmer. Since I don't use it unless I'm at crops, it has a bit of a learning curve again for me, and I find that I have to make sure I hold the paper tightly or it shifts.
The other two trimmers I have and rarely use are the Fiskars rotary trimmer. That's the really big one. I just don't have room for it, so it rarely comes out of the box. I do keep it for large projects, though, like I had to use it for a work project one time when I was cutting construction paper.
I also have that trimmer that was sold on tv years ago, with the little light in it. It's cheaply made, but it came with different shaped blades like a stamp edge and a wave edge that are fun to use on occasion, if I want a more subtle shape than what I'd get with a punch. The shapes it cuts are distinguishable from a straight edge, but they're not deep into the edge of the paper.
I have the purple cows 2-in-1 and I love it! It is big, but it is not heavy at all. I use the guillotine part more than the rotary side. I also have the mini (photo)fiskars guillotine trimmer for smaller projects and it is also awesome! I like that both cut straight. I used to use the cricut trimmer, but it started cutting crooked and funky even with a new blade.
I have several trimmers, most from several years ago except the most recent one from Martha Stewart, which I've been using lately for most single sheet cuts. My other trimmers include Fiskars straight-edge, as well as a couple of rotary trimmers. For cutting lots of papers at once, I rely on an old-fashioned wooden guillotine cutter. No blades to change, and it's quick and accurate.
I also have the purple cow 2 in 1, and love it! I got it at Costco several years ago for a great price, and last time I looked my Costco still carried them. I have found that I prefer guillotine cutters.
I don't think you can beat Fiskars. They are great products and their customer service is outstanding. A previous poster was right in saying the replacement blades are easy to find and a reasonable price. Even my 7 year old students love to use the Fiskars trimmer.