The following are sounds that you might like to download and use in your Scratch assignments.

ahhh.wav beat1.wav beat2.wav
bells.wav bong_bell_timer_hit_deep_01.ogg bounce_twang_spring_13.ogg
bzz.wav chomp.wav click.wav
ding.wav drop.wav electric_shock_zap_short_03.ogg
energy_gun.wav explosion.wav explosion_bang_04.ogg
explosion_crunch_000.ogg failure.wav fanfare.wav
force_field_000.ogg force_field_001.ogg force_field_002.ogg
force_field_003.ogg force_field_004.ogg hooray.wav
impact_metal_000.ogg impact_metal_blade_clang_01.ogg laser_large_000.ogg
laser_large_001.ogg laser_large_002.ogg laser_large_003.ogg
laser_large_004.ogg laser_retro_000.ogg laser_retro_001.ogg
laser_retro_002.ogg laser_retro_003.ogg laser_retro_004.ogg
laser_small_000.ogg laser_small_001.ogg laser_small_002.ogg
laser_small_003.ogg laser_small_004.ogg linus-song-loop.wav
metal_explosion.wav ow.wav ping.wav
proton.wav rooster.wav sad_trombone.wav
saturday-night-fever.wav shoot.wav slurp.wav
sound-sampler.py splat_crush_01.ogg success.wav
success_beeps_multi_echo_short_02.ogg success_cheers_win_chime_03.ogg success_chime_bells_sparkle_tune_05.ogg
success_pickup_collect_chime_01.ogg swipe_whoosh_double_01.ogg tech_charger_power_up_06.ogg
tech_weapon_gun_shot_phaser_down_02.ogg tock.wav vocal_cute_call_affection_03.ogg
vocal_evil_impact_hit_slash_04.ogg weapon_click_reload_mechanism_01.ogg weapon_gunshot_rifle_swish_02.ogg
woot.wav

You can also download this zip file that contains all of the sounds: sounds.zip