My Graflex Pacemaker 4x5. I just enjoy using it, and it's been through a bit of travel and such with me. Never really had a problem, it's been as reliable as a working German camera. I have a studio monorail I really like, but if I want to use large format, I usually end up just reaching for the Graflex. It's just more convenient.
Also on my favorites would be my Seagull 4BI. Bought it for about $50, just had the focus go out last year (but it's just offset by an adjustable amount, and only prevents me getting closer than two meters to my subject.) I paid way too much for it, but it's been used so much and worked so simply and easily that I have gotten more out of it than I paid for it. Would never tell someone to buy one though. It's sitting in my cabinet outside of its case (as it no longer fits in it with the bad focus) and I can take it out, and the shutter, aperture, film advance (everything except the focus) is in perfect working order. I can't say the same about my Rollei, sadly.
35mm, I'd have to say the Minolta SRT-101. I first learned on that camera, and it was the easiest thing I had ever used. Line the needle up in the ring and your exposure is set right. focus on the lens. Push the side button for depth of field preview. Nothing ever was bad with the camera, except the battery switch could be a little more user-friendly. Haven't used it in years, but I still have it around, perhaps mostly for sentimental reasons. I wouldn't hesitate to recommend one of them for someone who wants to try film photography.