Do NOT get all-metal knives if you work with anything slippery, etc. and frankly, folders are really very much a compromise if you really intend to use these for self-defense. VERY few folders are ideal for that purpose in any way or form, no matter how "tactical-looking" they may be.
If by tactical folders you mean - tactically styled - check below:
For lightweight (i..e ~3-4 oz.) avoid Zero Tolerance. Great knives, but definitely on the heavy size. IIRC, the Spyderco Manix and Chinook - both superb prod. lockback folders, are also pretty heavy. If about 7-9 oz. and their size is okay with you, do consider them.
Choices: - do check the reviews here and on youtube
Spyderco Military or Para-Military (pretty much the EASIEST to open no matter what, gloves, very lightweight, etc) and lock up nicely. The Police 3 or Rookie are other good choices. The Military and Police have about 4 inch blades though. All of them are designed to cut and slice well, as well as having somewhat thin tips for precision work. I personally think the P'kal is the best choice if you like edge-in methods for actual SD.
Benchmade 710 - very slim, decent locking system, VERY smooth. Recurve can annoy some during sharpening. Others from BM include the 520 and 610 and HK 14205. Some find the detent on Axis-lock folders to be too loose, but you will PROBABLY mostly use your knives for utility tasks, these are great for their low-profile open and closed, and very smooth, rapid opening.
Kershaw: Offset, Skyline, Tyrade, and Blur come to mind. The Skyline is probably the small utility folder you never knew you had to have

. Consider the OD-1, Zing, and Groove as well. The PackRat looks like a winner, though I haven't handled it yet.
Personally:
Military and Para-Military are pretty much the peak of the middle-line production folders for utility - lightweight, great blade design/geometry, handle ergos, and decent locks. They do lose a lot in terms of style, slimness (especially closed), and being "tacticool". If style and slimness is a bit more of a priority for you, then Benchmades and Kershaws are definitely brands you want to look at - great style, quality, etc. - but usually not quite the cutters that most Spydercos are

. That said, there are some very nice designs from both companies.
That said, I carry my cheapies more than my Sebbies, my Caly 3 ZDP, etc. Kershaw Skyline and Spyderco Tenacious have worked great for me, good grip, decent liner-lock, and nice action with enough detent that I don't have to worry even if dropped. Others include my Boker CLB Trance, M-Type, Hyper, and occasionally, the Direkt. In most environments, I carry a Keycom and a Subcom F.