Squirt Sealant - 1L
Squirt Sealant is a long life span sealant at a decent price. It contains a mix of latex and microfibres to which you add "beadblock" particles to so that you're covered for a wide range of hole sizes (apparently up to 6mm). Unlike some other sealants, it doesn't clump in the bottle even after being open for months.
Like all sealants, make sure you shake it properly before use, otherwise the particulates might remain in the bottle (they settle after a while).