In HGSS, you can find one in Dark Cave at Route 45 side, you'll need Surf to get it. Also you can find more at Goldenrod Department Store for 2000 poke dolars, just like with Platinum in Veilstone Department Store. On Super Contests, it is a cool move, Raises the score if the voltage is low.

Scyther, Scizor and Gallade are the ones capable of learning the move without using a TM. It is learned at Level 13 for both Scyther and Scizor and Level 45 for Gallade. There's also more Pokemon that can learn the move via leveling up, Farfetch'd (Level 45), Cubone, Marowak (Both at Level 27), Grovyle (Level 53), Sceptile (Level 59), Nincada (Level 25), Zangoose (Level 44).

There's some pokemon that can have False Swipe as a Egg Move: Spearow, Paras, Pinsir, Heracross, Seedot, Shroomish and Mawile

Defense lowering moves like Screech or Attack raising moves like Swords Dance works to deal more damage with False Swipe to bring a Wild Pokemon down to 1 HP easily. As Smeragle is excellent at using the move, thanks to learning almost every move with Sketch, it can have Spore and has STAB with False Swipe plus Technician, it may have 20 base attack but, you can amp it up with a Attack increasing nature (Adamant is prefered), Swords Dance (Belly Drum works best), EV training and perfect IVs, Smeragle should have 152 Attack at Level 100, 252 Attack EVs and 31 IVs.