A short video on how to add custom effects onto weapons/tools in vanilla Minecraft 1.8!! I used command blocks with scoreboards and some neat commands.

--- Commands used ---

Setup: /scoreboard objectives add effects stat.useItem.minecraft.iron_sword

Command connected to the output: /scoreboard players remove @p[score_effects_min=1] effects 1

Effect command: /effect @p[score_effects_min=1] minecraft:strength 60

Effect command II: /effect @p[score_effects_min=1] minecraft:speed 60 2

Give command: /give @p[score_effects_min=1] minecraft:golden_apple 1 1

Diamond sword: /scoreboard objectives add effects2 stat.useItem.minecraft.diamond_sword

Diamond sword command connected to output: /scoreboard players remove @p[score_effects2_min=1] effects2 1

Diamond sword effect command: /effect @p[score_effects2_min=1] minecraft:jump_boost 5 100

All effect ids: http://www.minecraftuniversity.com/status_effects_list/

Hope it helped! :)