To remove gaffer tape residue from cable use WD40. Spray WD40 onto your rag and apply to residue. Allow a few minutes to let the WD40 work. Wipe clean.
Use Mr Min on your DVDs to improve playback quality. Mr Min when applied evenly and lightly polished off fills hairline scratches.
Never spray lens cleaner directly onto your lens. Rather spray onto your cloth and then work on the lens.